The nucleophilic properties of cobalt salen complexes are examined using density functional theory to investigate its carbon fixing capacity. In particular, carbon dioxide attack on neutral and anionic cobalt salen molecules is considered. Carbon fixation occurs for the anionic cobalt salen complex and is due to the nucleophilic interaction between the cobalt center and carbon dioxide molecule in a Co dz{\texttwosuperior}{\textendash}CO$_{2}$ π* interaction. A minimum energy path search by a nudged elastic band calculation reveals a lower forward activation energy for the anionic complex than the neutral complex, indicating that the formation of the anionic complex is thermodynamically and kinetically favored. In this case, the CO$_{2}$ molecule is chemisorbed as partial charge transfer from the cobalt center to carbon dioxide is observed. Proposed reaction mechanisms explain how the Co{\textendash}C bond energy of the CO$_{2}${\textendash}cobalt salen complex can be tuned by appropriate substitutions of electron donating or withdrawing groups on the phenyl ring.

}, doi = {10.1039/C9RA01990A}, author = {Meliton R. Chiong and Francis N. C. Paraan} } @inproceedings {esperanzaSPP2019, title = {Critical scaling at the N{\'e}el transition in an extended Hubbard model with Ising-like interaction}, booktitle = {Proceedings of the 37th Samahang Pisika ng Pilipinas Physics Conference}, year = {2019}, month = {29 May 2019}, pages = {SPP-2019-1G-05}, address = {Tagbilaran City, Philippines}, abstract = {We examine the critical behavior of the von Neumann entanglement entropy and the staggered magnetization order parameter in an extended Hubbard chain across the N{\'e}el transition at half-filling. The order parameter and the entanglement entropy was calculated using density matrix renormalization group (DMRG) for periodic chains with length L = 32, 64, and 100. We demonstrate that the entanglement entropy can locate the quantum critical point. Finite size scaling analyses of the N{\'e}el order parameter and entanglement entropy give estimates for the critical exponents associated with these observables.}, url = {https://paperview.spp-online.org/proceedings/article/view/SPP-2019-1G-05}, author = {Robertson C. Esperanza and Francis N. C. Paraan} } @inproceedings {gomezSPP2019, title = {Evaporation and compaction of colliding dust clusters at different impact parameters}, booktitle = {Proceedings of the 37th Samahang Pisika ng Pilipinas Physics Conference}, year = {2019}, month = {29 May 2019}, pages = {SPP-2019-PB-21}, address = {Tagbilaran City, Philippines}, abstract = {The dynamics of colliding dust clusters is important in the study of dust cloud evolution. In this work, a molecular dynamics simulation of the collision of two spherical clusters of SiO2 particles was done to find out how the evaporation fraction depends on impact parameter. By measuring the average number of neighbors each unevaporated grain has, we found a critical impact parameter that results in maximum cluster compaction.}, url = {https://paperview.spp-online.org/proceedings/article/view/SPP-2019-PB-21}, author = {Jacob Gomez and Francis N. C. Paraan} } @inproceedings {535, title = {Ground state entanglement in an extended Hubbard model with Ising-like interactions}, booktitle = {AQIS Conference 2019 Abstract Booklet - Poster Day 1}, year = {2019}, month = {19{\textendash}23 Aug 2019}, pages = {164}, address = {Korea Institute for Advanced Study, Seoul}, abstract = {We probe the half-block von Neumann entanglement entropy along with the ground state properties of a 1D extended Hubbard model as its intrasite and intersite interaction parameters are varied. The half-block entanglement entropy was calculated using the density matrix renormalization group (DMRG) for a periodic chain. We demonstrate that the half-block entanglement entropy provides a sketch of the changes in the ground state of the system and that it can be used to locate the quantum critical lines in the model.}, url = {http://aqis-conf.org/2019/program/}, author = {Robertson C. Esperanza and Francis N. C. Paraan} } @inproceedings {lopezSPP2019, title = {Image preprocessing with bi-histogram equalization in a supervised classification of radiographs}, booktitle = {Proceedings of the 37th Samahang Pisika ng Pilipinas Physics Conference}, year = {2019}, month = {29 May 2019}, pages = {SPP-2019-PA-22}, address = {Tagbilaran City, Philippines}, abstract = {Convolutional neural network models are known for their effectiveness in solving computer vision problems. These neural networks are designed to extract features from raw data for accurate classification. The objective of this paper is to study the effects of bi-histogram equalization preprocessing on the performance of a convolutional neural network in identifying pneumonia from a chest x-ray image. The model trained with the preprocessed images demonstrated improved accuracy during training and validation of the neural network.}, url = {https://paperview.spp-online.org/proceedings/article/view/SPP-2019-PA-22}, author = {Vidal Wyatt M. Lopez and Francis N. C. Paraan} } @inproceedings {ongkikoSPP2019, title = {Molecular projected band structure of ammonia and ammonium adsorbed on graphene}, booktitle = {Proceedings of the 37th Samahang Pisika ng Pilipinas Physics Conference}, year = {2019}, month = {29 May 2019}, pages = {SPP-2019-PA-17}, address = {Tagbilaran City, Philippines}, abstract = {The electronic structures of ammonia and ammonium molecules adsorbed on pristine graphene are studied in this work. In particular, molecular projected densities of states (MolPDOS) were calculated by density functional theory to characterize these adsorption systems by projecting the eigenstates of the full system onto those of the adsorbate molecule. Ammonium adsorption on graphene exhibited a stronger adsorption than ammonia, indicating the possibility of designing a selective substrate. This difference was also reflected in the MolPDOS-produced band structure by the presence of distinct regions of mixed ammonium and graphene states located around 1 eV above the Fermi level.}, url = {https://paperview.spp-online.org/proceedings/article/view/SPP-2019-PA-17}, author = {Mario Antonio T. Ongkiko and Francis N. C. Paraan} } @inproceedings {castroSPP2019, title = {Multi-class semantic segmentation and volume calculation of cardiac CT scans using convolutional neural networks}, booktitle = {Proceedings of the 37th Samahang Pisika ng Pilipinas Physics Conference}, year = {2019}, month = {29 May 2019}, pages = {SPP-2019-1C-07}, address = {Tagbilaran City, Philippines}, abstract = {Computed tomography (CT) scans from the MICCAI 2017 Multi-Modality Whole Heart Segmentation Challenge dataset were segmented into seven anatomical substructures (left and right ventricles, left and right atria, myocardium, aorta, and pulmonary artery) using the SpatialConfiguration-Net (SCN). The SCN utilizes a U-Net convolutional network architecture that is designed for biomedical image segmentation. The performance of the neural network was evaluated by cross validation on the training data by the Dice Similarity Coefficient over all heart substructures. Improved segmentation of most of the substructures was observed over other proposed convolutional neural network pipelines. While the estimated volumes of the segmented substructures are consistent with the manual annotations, the SCN performed sub-optimally in detecting gaps between heart substructures due to the loss of resolution caused by multilayer down-sampling and up-sampling of the images.}, url = {https://paperview.spp-online.org/proceedings/article/view/SPP-2019-1C-07}, author = {Marc Jerrone Castro and Francis N. C. Paraan} } @inproceedings {deleonSPP2019, title = {Parallel acceleration of density matrix renormalization group calculations with TensorFlow}, booktitle = {Proceedings of the 37th Samahang Pisika ng Pilipinas Physics Conference}, year = {2019}, month = {29 May 2019}, pages = {SPP-2019-PB-14}, address = {Tagbilaran City, Philippines}, abstract = {We parallelize singular value decomposition in a matrix product state formulation of the density matrix renormalization group using the TensorFlow library to find use cases in which consumer-grade GPU hardware can reduce run times. Specifically, we tested the performance of the implementation on a 20-site spin chain for a variable number of kept states. We were able to acquire a speedup of up to 6.4\% when using TensorFlow GPU libraries and a speedup of up to 5.4\% with TensorFlow multicore CPU libraries. This speedup is observed when the number of kept states exceeds a threshold value so that the dimensions of the matrices in the calculation are large enough that the gains in parallelization exceed computational overhead costs.}, url = {https://paperview.spp-online.org/proceedings/article/view/SPP-2019-PB-14}, author = {Kryzz Joshua G. de Leon and Francis N. C. Paraan} } @inproceedings {536, title = {Quantum phase transitions and Schmidt gap closing in a Kitaev chain with long-ranged interactions}, booktitle = {AQIS Conference 2019 Abstract Booklet - Poster Day 1}, year = {2019}, month = {19{\textendash}23 Aug 2019}, pages = {174-175}, address = {Korea Institute for Advanced Study, Seoul}, abstract = {The quantum phase diagram of a generalized Kitaev chain that exhibits long-ranged hopping and pairing is mapped out by looking for sharp changes in the Schmidt gap of a ground state bipartition.Finite-size scaling analysis reveals that the Schmidt gap exhibits universal scaling behavior about the quantum critical lines. The critical exponents found shows that the model displays different properties at the long- and short-range limits of the interaction.}, url = {http://aqis-conf.org/2019/program/}, author = {Cleofe Dennielle P. Ayang-ang and Francis N. C. Paraan} } @article {498, title = {Strong chemisorption of CO$_{2}$ on B$_{1}$$_{0}${\textendash}B$_{1}$$_{3}$ planar-type clusters}, journal = {J. Phys. Condens. Matter}, volume = {31}, year = {2019}, pages = {145504}, abstract = {An ab initio density functional study was performed investigating the adsorption of CO$_{2}$ on neutral boron Bₙ (n = 10{\textendash}13) clusters that are characterized by planar and quasiplanar ground-state atomic structures. For all four clusters, we found large chemisorption binding energies, reaching 1.6 eV between CO$_{2}$ and B$_{1}$$_{2}$, with the adsorbed molecule oriented in the plane of the cluster and adsorbed along the cluster edge. A configuration with chemisorbed dissociated CO$_{2}$ molecule also exists for B$_{1}$$_{1}$ and B$_{1}$$_{3}$ clusters. The strong adsorption is due to the bending of the CO$_{2}$ molecule, which provides energetically accessible fully in-plane frontier molecular orbitals matching the edge states of the clusters. At the same time, the intrinsic dipole moment of a bent CO$_{2}$ molecule facilitates the transfer of excess electronic charge from the cluster edges to the molecule.

}, doi = {10.1088/1361-648x/aafebd}, author = {Alexandra B. Santos-Putungan and Nata{\v s}a Stoji{\'c} and Nadia Binggeli and Francis N. C. Paraan} } @conference {479, title = {Accuracy of a tensor network-based image classifier saturates with bond dimension}, year = {2018}, month = {18{\textendash}19 June 2018}, pages = {P126}, publisher = {ASTHRDP Graduate Scholars{\textquoteright} Conference}, address = {PICC, Pasay City}, abstract = {In the field of physics, tensor networks have been successfully applied to solve for problems requiring high-dimensionality. As data required in data science are also high-dimensional, tensor methods have also gained appreciation as a tool in machine learning. In this study, we have utilized an existing tensor network-based machine learning program to investigate on the role of bond dimension in the learning rate and the learning accuracy in an image classification problem. In our simulation, the increase in bond dimension leads to improved accuracy but easily reached a saturation point where the gains are overshadowed by the computational cost.}, author = {Mykhal Gideoni L. Mangada and Francis N. C. Paraan} } @inproceedings {canoy, title = {Average work done in a ground state quantum quench of the Kitaev chain model with variable-range interactions}, booktitle = {Proceedings of the 36th Samahang Pisika ng Pilipinas Physics Conference}, year = {2018}, month = {6{\textendash}9 June 2018}, pages = {SPP-2018-PC-18}, address = {Puerto Princesa City, Philippines}, abstract = {We study the average work done associated with a ground state quantum quench of the Kitaev chain model with variable-range interactions. We do this by initially preparing an isolated quantum system in the ground state of the initial Hamiltonian at zero temperature. We, then, abruptly change the relative chemical potential parameter. The average work done on the system, which is defined as the difference between the measured energies before and after the quench, is derived and shown to have inflection points at the critical values of the relative chemical potential of the initial Hamiltonian.}, url = {https://paperview.spp-online.org/proceedings/article/view/SPP-2018-PC-18}, author = {Raymart Jay E. Canoy and Francis N. C. Paraan} } @inproceedings {476, title = {Band structure contribution of adsorbed H2 on graphene calculated from molecular orbital projections}, booktitle = {Proceedings of the 36th Samahang Pisika ng Pilipinas Physics Conference}, year = {2018}, month = {6{\textendash}9 June 2018}, pages = {SPP-2018-PA-19}, address = {Puerto Princesa City, Philippines}, abstract = {Density functional theory allows for the first-principles calculation of projected wavefunctions onto orthogonalized atomic wavefunctions. Such calculations can be applied to study the bonding of a molecule onto an adsorbing surface. In particular, these projections allow one to identify the contributions of the adsorbed molecule to the band structure of the whole system. In this paper, we consider a system composed of an H_{2} molecule adsorbed onto the hollow (H) site in a graphene 3x3 supercell. The adsorbed H_{2} molecule gives rise to two bands roughly 6 eV on either side of the Fermi energy. These bands may be attributed to the hybridization of the H_{2} bonding and anti-bonding molecular\ σ\ orbitals and the graphene bands.

We examine a possible mechanism for the electrochemical reduction of carbon dioxide to carbon monoxide with cobalt salen complex, Co(salen), as the catalyst. Density functional theory was used to calculate the ground state energies and reaction energies of possible reaction intermediates. The results indicate that the reduction from [Co(salen)-CO_{2}]^{-} to Co(salen)-CO proceeds via a Co(salen)-COOH intermediate through a proton transfer and a subsequent concerted proton-electron transfer that releases one molecule of water. The catalyst is then regenerated after carbon monoxide dissociates from the complex.

The proper piezoelectric tensor of AlN was determined using the changes of the Berry phases in response to axial and shear strains in the linear regime. Phases arose from the variation of the wavevector of the Bloch states. Calculations were done in the Quantum ESPRESSO software package using Vanderbilt{\textquoteright}s formulation of the proper piezoelectric tensor. The maximum longitudinal piezoelectric modulus |eij|_{max} coefficient of 1.461 C/m^{2} was found when both the change in the Berry phase and strain were along the c-axis.

We perform density functional theory (DFT) based calculations to investigate the reduction of carbon dioxide CO_{2} to carbon monixide CO using a cobalt-Schiff base catalyst, Co(salen). DFT calculated formation energies and reduction potentials showed that CO_{2} is reduced to CO via a [Co(salen)-COOH] intermediate. The first step of the mechanism involves the reduction of electrically neutral [Co(salen)]\ to [Co(salen)]^{-\ }anion, followed by an electrophilic addition of CO_{2}. Furthermore, the sigma bond formed between cobalt metal center and\ CO_{2}\ involves a back-donation and partial charge transfer from cobalt to carbon. [Co(salen)-COOH] is further reduced to [Co(salen)-CO] and CO is released from the catalyst along with water H_{2}O.

We report distinctive nonanalytic signatures in the spin{\textendash}orbit entanglement of a 2D electron gas with Rashba interactions at integer values of the filling factor and at certain level crossings. The accompanying sharp changes in the bulk spin{\textendash}orbit entanglement entropy can be probed by measuring the fluctuation in the transverse spin polarization of the electron gas.

}, doi = {10.1088/1742-5468/2016/05/053104}, author = {Rona F Barbarona and Francis N. C. Paraan} } @inproceedings {309, title = {Investigation of neutral B13 clusters: A density functional theory study}, booktitle = {Proceedings of the 34th Samahang Pisika ng Pilipinas Physics Congress}, year = {2016}, month = {18{\textendash}21 Aug 2016}, pages = {SPP-2016-PA-18}, address = {University of the Philippines Visayas, Iloilo City}, abstract = {We investigate the electronic structure of neutral boron_13 (B13) clusters using spin-polarized density functional theory (DFT). The stable B13 cluster is observed to have a two-dimensional planar structure. Energy levels diagram shows that it has a highest occupied molecular orbital{\textendash}lowest unoccupied molecular orbital (HOMO-LUMO) gap of 0.36 eV. Analysis of the electronic charge density of the B13 cluster reveals that most of the electrons are shared between B atoms and are located at the edges, where the HOMO and LUMO are also localized. Our results indicate that the most reactive part of the cluster is along its edges.}, author = {Alexandra B. Santos-Putungan and Nata{\v s}a Stoji{\'c} and Nadia Binggeli and Francis N. C. Paraan} } @inproceedings {332, title = {Loschmidt amplitude zeros as a probe for criticality in the quenched XY model}, booktitle = {Proceedings of the 34th Samahang Pisika ng Pilipinas Physics Congress}, year = {2016}, month = {18{\textendash}21 Aug 2016}, pages = {SPP-2016-5C-06}, address = {University of the Philippines Visayas, Iloilo City}, abstract = {This paper investigates the correspondence between dynamical phase transitions (DPT) and quenches across quantum critical points (QCP) in ground state quenches of a spin-1/2 XY model. These DPTs are identified by treating the wavefunction overlap between pre- and post-quench states as a partition funtion and determining its Fisher zeros. It is found that DPTs do not always occur when the quench crosses a quantum critical line. A general condition for the occurrence of these DPTs in the XY model is derived.}, author = {Jan Philippe B. Sambo and Francis N. C. Paraan} } @inproceedings {322, title = {Molecular dynamics of rapid melting in a copper-silver alloy}, booktitle = {Proceedings of the 34th Samahang Pisika ng Pilipinas Physics Congress}, year = {2016}, month = {18{\textendash}21 Aug 2016}, pages = {SPP-2016-PA-22}, address = {University of the Philippines Visayas, Iloilo City}, abstract = {A copper-silver alloy (64\% Cu / 36\% Ag atomic ratio) is simulated by molecular dynamics. The alloy is subjected to rapid linear heating protocols from room temperature to 2100 K at several ramp rates of the order ~K/ps. Numerical evidence for a first-order melting transition at 1.19 x 10^3 K is observed. This elevated value is suggested to be the result of high pressures in the microscopic sample.}, author = {Cleofe Dennielle P. Ayang-ang and John Joseph S Solo and Zed Harold E. Fernandez and Francis N. C. Paraan} } @inproceedings {311, title = {Molecular dynamics simulation of liquid gallium using an embedded atom model}, booktitle = {Proceedings of the 34th Samahang Pisika ng Pilipinas Physics Congress}, year = {2016}, month = {18{\textendash}21 Aug 2016}, pages = {SPP-2016-5B-03}, address = {University of the Philippines Visayas, Iloilo City}, abstract = {Optimized embedded atom model (EAM) potential parameters from the literature are used to perform a molecular dynamics simulation of liquid gallium. Liquid densities are calculated at several temperatures at a fixed pressure of 1 atm to determine the mean coefficient of thermal expansion. Radial pair distribution functions showing the shell structure of the liquid phase are also obtained and compared with previous simulations and experimental results.}, author = {Oliver B. Generalao and Allan Jay Pari{\~n}as and Francis N. C. Paraan} } @inproceedings {314, title = {Multispecies fluid flow simulations inside a chamber via computational fluid dynamics}, booktitle = {Proceedings of the 34th Samahang Pisika ng Pilipinas Physics Congress}, year = {2016}, month = {18{\textendash}21 Aug 2016}, pages = {SPP-2016-2C-04}, address = {University of the Philippines Visayas, Iloilo City}, abstract = {Computational fluid dynamics simulations of silane inside a two-dimensional container filled with nitrogen gas were performed using finite element methods. Pressure gradients were introduced to the system, and the time needed for the system to reach dynamic equilibrium for mass fractions, pressure, and velocity was determined. The inlet size was also varied to determine how it affects the equilibriation time.}, author = {Apolinario Miguel Tan and Nicholas Christopher A Colina and Jennifer Anne Constantino and Francis N. C. Paraan} } @inproceedings {spvm-2016-1, title = {Observation of the behavior and properties of the critical micelle concentration (CMC) at different temperatures}, booktitle = {Proceedings of the 18th Samahang Pisika ng Visayas at Mindanao National Physics Conference}, year = {2016}, month = {20{\textendash}22 Oct 2016}, pages = {13}, address = {Silliman University, Dumaguete City}, author = {Allan Jay L Pari{\~n}as and John Joseph S Solo and Lloyd Francis L Co and Francis N. C. Paraan} } @inproceedings {310, title = {Parallelization benchmarks of plane wave self-consistent field calculations on an IBM BlueGene supercomputer}, booktitle = {Proceedings of the 34th Samahang Pisika ng Pilipinas Physics Congress}, year = {2016}, month = {18{\textendash}21 Aug 2016}, pages = {SPP-2016-PB-19}, address = {University of the Philippines Visayas, Iloilo City}, abstract = {A plane wave self-consistent field calculation was parallelized over two node cards of an IBM BlueGene/P supercomputer. A maximum speedup of 9x was measured in Virtual Node execution mode. The observed performance improvements are consistent with Amdahl{\textquoteright}s law for an algorithm that is approximately 89\% parallelizable.}, author = {Paul Daniel S. Ang and Lean Louiel A Peria and Joshua Gregor A Dizon and Francis N. C. Paraan} } @inproceedings {331, title = {Piezomagnetic properties and band structure of Mn3GaN calculated using density functional theory}, booktitle = {Proceedings of the 34th Samahang Pisika ng Pilipinas Physics Congress}, year = {2016}, month = {18{\textendash}21 Aug 2016}, pages = {SPP-2016-3A-06}, address = {University of the Philippines Visayas, Iloilo City}, abstract = {The antiperovskite Mn3GaN in the Γ-5g configuration has a noncollinear magnetic ordering and exhibits the piezomagnetic effect. This study aims to replicate previous ab initio studies of Mn3GaN. Magnetic moments are allowed to relax after applying various amounts of strain. Results show that the total magnetization varies linearly with strain up to {\textpm}2\%. The observed response of the magnetization was stronger for negative strain than for positive strain. Calculations reveal that this net magnetization arises from the strain-induced rotation of the local magnetic moments associated with each Mn atom. In addition, numerical calculations of the band structure and density of states of Mn3GaN are presented.}, author = {Lean Louiel A Peria and Paul Daniel S. Ang and Francis N. C. Paraan} } @conference {351, title = {Polarization fluctuation as an entanglement measure for N-level systems}, year = {2016}, month = {7{\textendash}8 Apr 2016}, pages = {127}, publisher = {1st International DOST-SEI ASTHRDP-NSC Scholars{\textquoteright} Conference}, address = {PICC, Pasay City}, abstract = {It is known that subsystem fluctuations are related to entanglement for any N-level system entangled with an environment. We define an observable wherein its fluctuations can be directly related to known measures such as the purity, R{\'e}nyi-2 entropy, and concurrence. This quantity, which we call the Schmidt polarization fluctuation shows an exact relationship between fluctuations and entanglement that is simple to construct and is model-independent. It can also be considered as a proper entanglement measure and is experimentally accessible.}, author = {Aura Mae B Villaruel and Francis N. C. Paraan} } @conference {325, title = {Quantum criticality in a quenched XY chain}, year = {2016}, month = {25{\textendash}27 Jul 2016}, publisher = {Conference on Entanglement and Non-Equilibrium Physics of Pure and Disordered Systems}, address = {International Centre for Theoretical Physics, Trieste}, url = {http://indico.ictp.it/event/7604/}, author = {Francis A Bayocboc Jr and Jan Philippe Sambo and Francis N. C. Paraan} } @conference {paraan-qpcmp-2016, title = {Quenched spin chains and generalized Gibbs ensembles}, year = {2016}, month = {18{\textendash}19 Apr 2016}, publisher = {Workshop on Theories in Quantum Phenomena and Condensed Matter Physics}, address = {University of the Philippines Los Ba{\~n}os, Laguna}, url = {https://imsp.uplb.edu.ph/index.php/23-imsp-news/training-and-conference/386-quantum-phenomena-workshop}, author = {Francis N. C. Paraan} } @inproceedings {spvm-2016-2, title = {Structural analysis and visualization of spatial distribution of electrons of pristine and alkali metal-doped polythiophene}, booktitle = {Proceedings of the 18th Samahang Pisika ng Visayas at Mindanao National Physics Conference}, year = {2016}, month = {20{\textendash}22 Oct 2016}, pages = {23}, address = {Silliman University, Dumaguete City}, author = {Prudence Peace V Bustamante and Melchor J Potestas and Francis N. C. Paraan} } @conference {371, title = {Zeros of the Loschmidt amplitude in the quenched XY model}, year = {2016}, month = {4{\textendash}8 Dec 2016}, pages = {CSCMP 48}, publisher = {Joint 13th Asia Pacific Physics Conference and 22nd Australian Institute of Physics Congress}, address = {Brisbane, Australia}, abstract = {We investigate the notion of dynamical quantum phase transitions (DQPTs) in the quenched ground state of the spin-1/2 XY model H(h0, γ0) to H(h1, γ1). By a Wick rotation, the Loschmidt amplitude is formally treated as a canonical partition function and its zeros used as a probe for criticality. This approach is similar to that used in a Fisher zero analysis in identifying classical phase transitions. The occurrence of real-time zeros for the Loschmidt amplitude signify DQPTs. Previously, a correspondence between DQPTs and quenches across critical points was observed for the transverse-field Ising model. The zeros of the Loschmidt amplitude in a quench of the XY model ground state was calculated and the corresponding condition for a DPQT to occur was derived for a generic quench. It can be observed that not all quenches across critical points are accompanied by DQPTs and vice versa. This result is consistent with previous studies of the quenched XY model.}, url = {http://aappsbulletin.org/myboard/read.php?Board=others\&id=100}, author = {Jan Philippe Sambo and Francis N. C. Paraan} } @article {Seroje2015, title = {Effective thermodynamics of isolated entangled squeezed and coherent states}, journal = {Eur. J. Phys.}, volume = {36}, number = {5}, year = {2015}, pages = {055051}, abstract = {The R{\'e}nyi entanglement entropy is calculated exactly for mode-partitioned isolated systems such as the two-mode squeezed state and the multi-mode Silbey{\textendash}Harris polaron ansatz state. Effective thermodynamic descriptions of the correlated partitions are constructed to present quantum information theory concepts in the language of thermodynamics. Boltzmann weights are obtained from the entanglement spectrum by deriving the exact relationship between an effective temperature and the physical entanglement parameters. The partition function of the resulting effective thermal theory can be obtained directly from the single-copy entanglement.}, doi = {10.1088/0143-0807/36/5/055051}, author = {King Karl R Seroje and Rafael S dela Rosa and Francis N. C. Paraan} } @inproceedings {santosputungan-spp-2015, title = {Enhanced ferromagnetism in Zn0.5 (Co)0.5 O alloy: DFT calculations}, booktitle = {Proceedings of the 33rd Samahang Pisika ng Pilipinas Physics Congress}, year = {2015}, month = {3{\textendash}6 Jun 2015}, pages = {SPP-2015-PA-14}, address = {University of Northern Philippines, Vigan City}, abstract = {In this work, we studied the structure and magnetic properties of Zn0.5(Co)0.5O alloy via spin-polarized density functional theory DFT. We utilized a 1 x 1 ZnO hexagonal wurtzite unit cell in a 4-atom bilayer configuration, with one Zn atom replaced by a Co atom. We found that the original lattice parameters of ZnO did not change appreciably upon Co alloying, and thus the structure remains robust. Similarly, minimal charge redistribution between the metals and oxygen is observed. Lastly, our calculations showed that the net magnetization of ZnO upon Co alloying is enhance significantly, much larger than that via doping. The results suggest that\ Zn0.5(Co)0.5O\ as a ferromagnetic material is a potential candidate for advanced spintronic applications.

},
author = {Alexandra B. Santos-Putungan and Joshua Gregor A Dizon and Darwin B Putungan and Francis N. C. Paraan}
}
@inproceedings {delarosa-spp-2015,
title = {Entanglement entropy of the Silbey-Harris polaron ansatz for a spin-boson model},
booktitle = {Proceedings of the 33rd Samahang Pisika ng Pilipinas Physics Congress},
year = {2015},
month = {3{\textendash}6 Jun 2015},
pages = {SPP-2015-PB-47},
address = {University of Northern Philippines, Vigan City},
abstract = {We obtained the entanglement entropy between a qubit and a harmonic oscillator bath using a Silbey-Harris polaron ansatz. With the assumption that a single mode frequency is dominant, we calculated the exact dependence of the von Neumann entropy on the displacement parameter. The entanglement entropy increases and saturates exponentially fast to its maximum value of ln2 as the magnitude of the displacement increases. We also showed that the entanglement entropy depends on the sum of complex squares of each displacement when the bath is a multi-mode coherent state.

},
author = {Rafael S dela Rosa and Francis N. C. Paraan}
}
@inproceedings {laurente-spp-2015,
title = {Exact calculation of the average work done in a quenched quantum Ising model},
booktitle = {Proceedings of the 33rd Samahang Pisika ng Pilipinas Physics Congress},
year = {2015},
month = {3{\textendash}6 Jun 2015},
pages = {SPP-2015-PB-48},
address = {University of Northern Philippines, Vigan City},
abstract = {The main aim of this paper is to calculate the average work done in a ground state quench of the XY Heisenberg model in the transverse field quantum Ising limit. We obtain an exact closed form expression for the average work done in terms of complete elliptic integrals. This result reveals an inflection point at a pre-quench field that satisfies |h0|=1, which signals quantum criticality.

},
author = {Salvador T Laurente Jr and Francis N. C. Paraan}
}
@inproceedings {bayocboc-spp-2015,
title = {Exact expression for the work fluctuation in a quenched transverse field Ising chain},
booktitle = {Proceedings of the 33rd Samahang Pisika ng Pilipinas Physics Congress},
year = {2015},
month = {3{\textendash}6 Jun 2015},
pages = {SPP-2015-PA-48},
address = {University of Northern Philippines, Vigan City},
abstract = {We study the emergent thermodynamics associated with an arbitrary field quench in the Transverse Field Ising Model by calculating the fluctuations in the work done. An exact expression for the work fluctuation is obtained and is shown to exhibit non-analytic behavior when the system is initially critical.

},
author = {Francis A Bayocboc Jr and Francis N. C. Paraan}
}
@article {Bayocboc2015,
title = {Exact work statistics of quantum quenches in the anisotropic XY model},
journal = {Phys. Rev. E},
volume = {92},
number = {3},
year = {2015},
pages = {032142},
abstract = {We derive exact analytic expressions for the average work done and work fluctuations in instantaneous quenches of the ground and thermal states of a one-dimensional anisotropic XY model. The average work and a quantum fluctuation relation is used to determine the amount of irreversible entropy produced during the quench, eventually revealing how the closing of the excitation gap leads to increased dissipated work. The work fluctuation is calculated and shown to exhibit nonanalytic behavior as the prequench anisotropy parameter and transverse field are tuned across quantum critical points. Exact compact formulas for the average work and work fluctuation in ground state quenches of the transverse field Ising model allow us to calculate the first singular field derivative at the critical field values.},
doi = {10.1103/PhysRevE.92.032142},
author = {Francis A Bayocboc Jr and Francis N. C. Paraan}
}
@inproceedings {tacbad-spp-2015,
title = {Lateral motion of a spherical particle suspended in Couette flow},
booktitle = {Proceedings of the 33rd Samahang Pisika ng Pilipinas Physics Congress},
year = {2015},
month = {3{\textendash}6 Jun 2015},
pages = {SPP-2015-5C-04},
address = {University of Northern Philippines, Vigan City},
abstract = {This study aims to simulate the lateral motion of a neutrally buoyant spherical particle suspended in Couette flow using a lattice-Boltzmann algorithm. It was found that the particle migrates to an equilibrium position at the center of the channel regardless of its initial position. A force coupling constant controls the strength of particle and fluid interactions. Requiring this constant to enforce Stokes{\textquoteright} drag on the particle resulted in a slightly faster migration than when using a constant that conserves the net kinetic energy.

},
author = {Robert C Tacbad and Zed Harold E. Fernandez and Francis N. C. Paraan}
}
@conference {paraan-qpcmp-2015,
title = {Mode entanglement in BCS superconductivity, quantum optics, and quantum Hall physics},
year = {2015},
month = {22{\textendash}23 Apr 2015},
publisher = {Workshop on Theories in Quantum Phenomena and Condensed Matter Physics},
address = {University of the Philippines Los Ba{\~n}os, Laguna},
url = {https://imsp.uplb.edu.ph/index.php/component/content/article/17-imsp-news/research/370-workshop-on-theories-in-quantum-phenomena-and-condensed-matter-physics},
author = {Francis N. C. Paraan}
}
@inproceedings {321,
title = {Polarization fluctuation as an entanglement monotone for entangled two-level systems},
booktitle = {Proceedings of the AQIS Conference 2015},
year = {2015},
month = {24{\textendash}30 Aug 2015},
pages = {271-272},
address = {Korea Institute for Advanced Study, Seoul},
abstract = {In a pure system consisting of a two-level atom (qubit) entangled with an arbitrary environment, the polarization fluctuation about the Schmidt axis is shown to preserve majorization. This polarization fluctuation is additive over independent two-level systems and is proposed to be an experimentally accessible entanglement monotone for a generic gas of two-level atoms entangled with a common bath.},
url = {http://aqis-conf.org/2015/program/},
author = {Aura Mae B Villaruel and Francis N. C. Paraan}
}
@inproceedings {villaruel-spp-2015,
title = {Polarization fluctuation can partially order entangled qubit states},
booktitle = {Proceedings of the 33rd Samahang Pisika ng Pilipinas Physics Congress},
year = {2015},
month = {3{\textendash}6 Jun 2015},
pages = {SPP-2015-3B-03},
address = {University of Northern Philippines, Vigan City},
abstract = {We define and calculate the Schmidt polarization fluctuation of a qubit entangled with an arbitrary environment in a bipartite pure state. It is found that this polarization fluctuation preserves majorization and thus can partially order qubits. We propose that this quantity can be used as an experimentally accessible entanglement measure.

},
author = {Aura Mae B Villaruel and Francis N. C. Paraan}
}
@inproceedings {puspus-spp-2015,
title = {R{\'e}nyi entanglement entropy of the spin-partitioned BCS ground state},
booktitle = {Proceedings of the 33rd Samahang Pisika ng Pilipinas Physics Congress},
year = {2015},
month = {3{\textendash}6 Jun 2015},
pages = {spp-2015-2B-03},
address = {University of Northern Philippines, Vigan City},
abstract = {We use the R{\'e}nyi entanglement entropy to study entanglement between the spin components of the Bardeen-Cooper-Schrieffer (BCS) ground state and we characterize its limiting values. We show that R{\'e}nyi entropies peak in the region about the Fermi surface. We also show that the orbital single-copy entanglement can be interpreted as the thermodynamic free energy of a two-level system at thermal equilibrium. We observed that the total R{\'e}nyi-2 entropy and the total single-copy entanglement are proportional to the number of electron orbitals having energies about the Fermi energy.

},
author = {Xavier M Puspus and Francis N. C. Paraan}
}
@inproceedings {barbarona-spp-2015,
title = {Spin polarization and its fluctuation in a two-dimensional electron gas with Rashba spin-orbit interactions},
booktitle = {Proceedings of the 33rd Samahang Pisika ng Pilipinas Physics Congress},
year = {2015},
month = {3{\textendash}6 Jun 2015},
pages = {SPP-2015-5C-07},
address = {University of Northern Philippines, Vigan City},
abstract = {The total spin polarization of a two-dimensional gas in the presence of a transverse magnetic field and Rashba spin-orbit interaction vanishes at high filling factors (weak magnetic fields) and shows the location of level crossings at sudden changes in its values. At strong magnetic fields, non-analyticities in the behavior of the spin fluctuations are exhibited at half-integer filling factors.

},
author = {Rona F Barbarona and Francis N. C. Paraan}
}
@conference {352,
title = {Structural and magnetic properties of Zn0.5 Co0.5 O alloy configurations via DFT},
year = {2015},
month = {16{\textendash}18 June 2015},
pages = {56},
publisher = {8th Conference of Asian Consortium on Computational Materials Science},
address = {National Taiwan University of Science and Technology, Taipei},
abstract = {We studied the structure and magnetic properties of ZnCoO alloy configurations via spin-polarized density functional theory (DFT). For the hexagonal wurtzite Zn0.5(Co)0.5O alloy, we used a 1x1x1 ZnO unit cell in a 4-atom bilayer configuration, with one Zn atom replaced by Co. In a similar manner, we utilized a 1x1x1 CoO rocksalt structure, with four Co atoms replaced by Zn to obtain Co0.5(Zn)0.5O. We found that the original ZnO lattice did not change appreciably upon Co alloying, with around 2\% compression, and thus the structure remains robust and atoms bond stronger. This is complemented by Zn0.5(Co)0.5O stronger bulk cohesive energy per formula unit (8.29 eV) compared to bulk ZnO (7.05 eV). Additionally, minimal charge redistribution between the metal atoms and oxygen is observed. On another note, a volume expansion of 3\% was observed for Co0.5(Zn)0.5O, implying the formation of weaker bonds between atoms. The calculated bulk cohesive energy per formula unit for CoO is 9.47 eV, quite larger than that of Co0.5(Zn)0.5O at 8.07 eV. Lastly, our calculations showed that the net magnetization of ZnO upon Co alloying is enhanced significantly, while the reverse is true for Zn-alloyed
CoO. The results suggest that Zn0.5(Co)0.5O is more stable in hexagonal wurtzite structure and could be a better controllable ferromagnetic material for spintronics applications.},
url = {http://www.iams.sinica.edu.tw/accms8/program$\#$poster},
author = {Alexandra B. Santos-Putungan and Francis N. C. Paraan}
}
@conference {353,
title = {Work statistics in quantum quenches in the Heisenberg XY model},
year = {2015},
month = {9{\textendash}13 Mar 2015},
publisher = {Quantum many-body systems far from equilibrium: Quench dynamics, thermalisation, and cold-atom experiments},
address = {National Institute for Theoretical Physics, Stellenbosch},
url = {http://www.nithep.ac.za/4i5.htm},
author = {Francis A Bayocboc Jr and Francis N. C. Paraan}
}
@article {Puspus2014,
title = {Entanglement spectrum and number fluctuations in the spin-partitioned BCS ground state},
journal = {Phys. Rev. B},
volume = {90},
number = {15},
year = {2014},
note = {cited By 2},
pages = {155123},
abstract = {We study entanglement between the spin components of the BCS ground state by calculating the full entanglement spectrum and the corresponding von Neumann entanglement entropy. The entanglement spectrum is effectively modeled by a generalized Gibbs ensemble (GGE) of noninteracting electrons, which may be approximated by a canonical ensemble at the BCS critical temperature. We further demonstrate that the entanglement entropy is jointly proportional to the pairing energy and to the number of electrons about the Fermi surface (an area law). Furthermore, the entanglement entropy is also proportional to the number fluctuations of either spin component in the BCS state.

},
doi = {10.1103/PhysRevB.90.155123},
author = {Xavier M Puspus and Kristian Hauser Villegas and Francis N. C. Paraan}
}
@inproceedings {324,
title = {Integer effects in the spin-orbit entanglement entropy in a 2D electron system with Rashba interactions},
booktitle = {Proceedings of the AQIS Conference 2014},
year = {2014},
month = {20{\textendash}24 Aug 2014},
pages = {239-240},
address = {Kyoto University, Japan},
abstract = {The entanglement between spin and orbital degrees of freedom in a two-dimensional electron system with Rashba spin-orbit coupling displays non-analytic behavior at integer filling factors.},
url = {http://aqis-conf.org/2014/program/},
author = {Rona F Barbarona and Francis N. C. Paraan}
}
@inproceedings {tacbad-spp-2014,
title = {Lateral motion of a suspended spherical particle between two parallel moving walls},
booktitle = {Proceedings of the 32nd Samahang Pisika ng Pilipinas Physics Congress},
year = {2014},
month = {17{\textendash}20 Oct 2014},
pages = {SPP2014-PB-4},
address = {University of the Philippines Diliman, Quezon City},
abstract = {This study aims to determine the dynamics of a spherical particle that is suspended in a fluid that is confined between two parallel moving walls. A simulation was done using the molecular dynamics software LAMMPS. It was observed that the particle tends to move toward the wall nearer to it and that its equilibrium displacement is approximately proportional to its initial distance from the center. It was also observed that increasing the wall velocity increases the magnitude of this lateral displacement.

},
author = {Robert C Tacbad and Joshua Gregor A Dizon and Francis N. C. Paraan}
}
@inproceedings {delarosa-spp-2014,
title = {Mode entanglement in squeezed coherent and displaced squeezed states},
booktitle = {Proceedings of the 32nd Samahang Pisika ng Pilipinas Physics Congress},
year = {2014},
month = {17{\textendash}20 Oct 2014},
pages = {SPP2014-5A-7},
address = {University of the Philippines Diliman, Quezon City},
abstract = {We study mode entanglement in four quantum states (coherent state, squeezed vacuum state, displaced squeezed state, squeezed coherent state), which are generated from a bosonic two-mode vacuum state by the action of displacement and squeezing operators. The mode entanglement entropy in these states is calculated and shown to depend only on the squeezing magnitude.

},
author = {Rafael S dela Rosa and King Karl R Seroje and Francis N. C. Paraan}
}
@inproceedings {tabernilla-spp-2014,
title = {Speed-up and efficiency of parallelized Monte Carlo integration on homogeneous and heterogeneous clusters},
booktitle = {Proceedings of the 32nd Samahang Pisika ng Pilipinas Physics Congress},
year = {2014},
month = {17{\textendash}20 Oct 2014},
pages = {SPP2014-2C-6},
address = {University of the Philippines Diliman, Quezon City},
abstract = {We evaluate the performance of parallelized Monte Carlo integration algorithms on homogeneous and heterogeneous clusters of the Structure and Dynamics Laboratory. In this study, intrinsic pseudorandom number generators for Fortran and Python were used and parallelization achieved by MPI libraries. On an example using 10^9 samples, the parallelized Python code proved to be scalable on a cluster of up to 44 processors. The Fortran parallelized code performed less well on scalability but had a much shorter execution time. It was also observed that the overhead cost of parallelization saturates as the number of processors used increased.

},
author = {Ryan Carlos M Tabernilla and John Kevin R Sanchez and Francis N. C. Paraan}
}
@inproceedings {323,
title = {Work fluctuations in quantum quenches in the XY model},
booktitle = {Proceedings of the AQIS Conference 2014},
year = {2014},
month = {20{\textendash}24 Aug 2014},
pages = {193-194},
address = {Kyoto University, Japan},
abstract = {The emergent thermodynamics associated with quenching in the Heisenberg XY model is studied by calculating the fluctuations in the work done by an arbitrary quench. For certain post-quench parameters, non-analytic behavior in the work fluctuation as a function of pre-quench parameters can be used to locate the critical regions in the XY model phase diagram.},
url = {http://aqis-conf.org/2014/program/},
author = {Francis A Bayocboc Jr and Francis N. C. Paraan}
}
@inproceedings {puspus-spp-2013,
title = {Entanglement entropy of impenetrable bosons in 1D: Effects of block length and boundaries},
booktitle = {Proceedings of the 31st Samahang Pisika ng Pilipinas Physics Congress},
year = {2013},
month = {23{\textendash}25 Oct 2013},
pages = {SPP2013-3B-7},
address = {University of San Carlos, Cebu City},
abstract = {The effects of block length and boundary conditions on the entanglement entropy of two impenetrable bosons in separate spatial partitions of finite extent are studied in this paper. The von Neumann and R{\'e}nyi entropies decreased monotonically as the lengths of the block and environment become more and more unequal. Also, the system with periodic boundary conditions possesses a larger entanglement entropy than that with open boundaries.

},
author = {Xavier M Puspus and Francis N. C. Paraan}
}
@inproceedings {seroje-spp-2013,
title = {Entanglement spectrum and entropy of two-mode squeezed vacuum states},
booktitle = {Proceedings of the 31st Samahang Pisika ng Pilipinas Physics Congress},
year = {2013},
month = {23{\textendash}25 Oct 2013},
pages = {SPP2013-3B-6},
address = {University of San Carlos, Cebu City},
abstract = {Mode entanglement in a two-mode squeezed state is studied. The entanglement spectrum is derived and interpreted as Boltzmann coefficients of harmonic oscillator eigenstates at thermal equilibrium. The effective temperature is expressed in terms of squeezing parameters and is equal to zero when the state is unsqueezed and increases without bound as the state is infinitely squeezed. It is demonstrated that the reduced density operator can be identified as a canonical ensemble of single harmonic oscillator at some effective temperature Te. The R{\'e}nyi entanglement entropy is calculated and found to increase without bound as the squeezing parameter increases. The single-copy entanglement, which is a limiting value of the R{\'e}nyi entropy, is interpreted as a partition function.

},
author = {King Karl R Seroje and Francis N. C. Paraan}
}
@inproceedings {paraan-spp-2013,
title = {Entanglement, statistical mechanics, and parallel computing},
booktitle = {Proceedings of the 31st Samahang Pisika ng Pilipinas Physics Congress},
year = {2013},
month = {23{\textendash}25 Oct 2013},
pages = {SPP2013-PS-04},
address = {University of San Carlos, Cebu City},
abstract = {This talk has two parts. In the first, the concept of entanglement entropy in quantum information theory is presented in the context of principles of equilibrium statistical mechanics. The central object linking the two subjects is the reduced density operator. In the second part, a primer on two implementations of parallel computing in multisocket and multicore computers is given. Typical results of parallel programs using Message Passing Interface (MPI) and Open Multi-processing (OpenMP) are discussed to demonstrate the feasibility of parallel computing on desktop computers.

},
author = {Francis N. C. Paraan}
}
@inproceedings {tacbad-spp-2013,
title = {Parallel speed-up and efficiency in single loop sums and matrix multiplication},
booktitle = {Proceedings of the 31st Samahang Pisika ng Pilipinas Physics Congress},
year = {2013},
month = {23{\textendash}25 Oct 2013},
pages = {SPP2013-PB-09},
address = {University of San Carlos, Cebu City},
abstract = {This study aims to evaluate the performance of parallel implementations of single loop sums and matrix multiplication using the Message Passing Interface. Benchmark results were obtained from the available computing resources of the Structure and Dynamics Group (SanD). These implementations were run using 1 to 24 processors and their speed-up and efficiency were calculated. Nearly ideal speed up and efficiency was observed when tasks were distributed over physical cores of a single CPU.

},
author = {Robert C Tacbad and Francis N. C. Paraan}
}
@inproceedings {cosme-spp-2013,
title = {Thomas-Fermi approach on the particle density of a Tonks-Girardeau gas in harmonic confinement with multiple δ-perturbations},
booktitle = {Proceedings of the 31st Samahang Pisika ng Pilipinas Physics Congress},
year = {2013},
month = {23{\textendash}25 Oct 2013},
pages = {SPP2013-3B-2},
address = {University of San Carlos, Cebu City},
abstract = {We investigate the Thomas-Fermi approach on the single particle density of a strongly interacting one dimensional bose gas under harmonic confinement with multiple localized δ barriers. We compare the resulting approximate of the density profile to exact density profiles that can be calculated for finite number of bosons. From the ground state energy, the corresponding chemical potential at *T*=0 is used to find the radius or extent of the density cloud.

},
author = {Jayson G Cosme and Francis N. C. Paraan and Jose Perico H Esguerra}
}
@article {Santos2012,
title = {Entanglement spectra of q-deformed higher spin VBS states},
journal = {J. Phys. A: Math. Theor.},
volume = {45},
number = {17},
year = {2012},
note = {cited By 3},
pages = {175303},
abstract = {We calculate the reduced density matrix of a block of integer spin-*S*{\textquoteright}s in a *q*-deformed valence-bond-solid (VBS) state. This matrix is diagonalized exactly for an infinitely long block in an infinitely long chain. We construct an effective Hamiltonian with the same spectrum as the logarithm of the density matrix. We also derive analytic expressions for the von Neumann and R{\'e}nyi entanglement entropies. For blocks of finite length, we calculate the eigenvalues of the reduced density matrix by perturbation theory and numerical diagonalization. These results enable us to describe the effects of finite-size corrections on the entanglement spectrum and entropy in this generalized VBS model.

},
doi = {10.1088/1751-8113/45/17/175303},
author = {Raul A Santos and Francis N. C. Paraan and Vladimir E Korepin and Andreas Kl{\"u}mper}
}
@article {Santos2012,
title = {Entanglement spectra of the q-deformed Affleck-Kennedy-Lieb-Tasaki model and matrix product states},
journal = {Europhys. Lett.},
volume = {98},
number = {3},
year = {2012},
note = {cited By 4},
pages = {37005},
abstract = {We exactly calculate the reduced density matrix of matrix product states (MPS). Our compact result enables one to perform analytic studies of entanglement in MPS. In particular, we consider the MPS ground states of two anisotropic spin chains. One is a *q*-deformed Affleck-Kennedy-Lieb-Tasaki (AKLT) model and the other is a general spin-1 quantum antiferromagnet with nearest-neighbor interactions. Our analysis shows how anisotropy affects entanglement on different continuous parameter manifolds. We also construct an effective boundary spin model that describes a block of spins in the ground state of the *q*-deformed AKLT Hamiltonian. The temperature of this effective model is given in terms of the deformation parameter *q*.

},
doi = {10.1209/0295-5075/98/37005},
author = {Raul A Santos and Francis N. C. Paraan and Vladimir E Korepin and Andreas Kl{\"u}mper}
}
@article {Santos2012,
title = {Quantum phase transition in a multicomponent anyonic Lieb-Liniger model},
journal = {Phys. Rev. B},
volume = {86},
number = {4},
year = {2012},
note = {cited By 2},
pages = {045123},
abstract = {We study a one-dimensional multicomponent anyon model that reduces to a multicomponent Lieb-Liniger gas of impenetrable bosons (Tonks-Girardeau gas) for vanishing statistics parameter. At fixed component densities, the coordinate Bethe ansatz gives a family of quantum phase transitions at special values of the statistics parameter. We show that the ground-state energy changes extensively between different phases. Special regimes are studied and a general classification for the transition points is given. An interpretation in terms of statistics of composite particles is proposed.

},
doi = {10.1103/PhysRevB.86.045123},
author = {Raul A Santos and Francis N. C. Paraan and Vladimir E Korepin}
}
@article {Paraan2011,
title = {Entanglement in bipartite pure states of an interacting boson gas obtained by local projective measurements},
journal = {Phys. Rev. A},
volume = {84},
number = {3},
year = {2011},
note = {cited By 1},
pages = {032330},
abstract = {We quantify the extractable entanglement of excited states of a Lieb-Liniger gas that are obtained from coarse-grained measurements on the ground state in which the boson number in one of two complementary contiguous partitions of the gas is determined. Numerically exact results obtained from the coordinate Bethe ansatz show that the von Neumann entropy of the resulting bipartite pure state increases monotonically with the strength of repulsive interactions and saturates to the impenetrable-boson limiting value. We also present evidence indicating that the largest amount of entanglement can be extracted from the most probable projected state having half the number of bosons in a given partition. Our study points to a fundamental difference between the nature of the entanglement in free-bosonic and free-fermionic systems, with the entanglement in the former being zero after projection, while that in the latter (corresponding to the impenetrable-boson limit) being nonzero.

}, doi = {10.1103/PhysRevA.84.032330}, author = {Francis N. C. Paraan and Javier Molina-Vilaplana and Vladimir E Korepin and Sougato Bose} } @article {Paraan2010, title = {Perturbative correction to the ground-state properties of one-dimensional strongly interacting bosons in a harmonic trap}, journal = {Phys. Rev. A}, volume = {82}, number = {6}, year = {2010}, note = {cited By 2}, pages = {065603}, abstract = {We calculate the first-order perturbation correction to the ground-state energy and chemical potential of a harmonically trapped boson gas with contact interactions about the infinite repulsion Tonks-Girardeau limit. With *c* denoting the interaction strength, we find that, for a large number of particles *N*, the 1/*c* correction to the ground-state energy increases as *N*^^{5/2}, in contrast to the unperturbed Tonks-Girardeau value that is proportional to *N*^^{2}. We describe a thermodynamic scaling limit for the trapping frequency that yields an extensive ground-state energy and reproduces the zero temperature thermodynamics obtained by a local-density approximation.

},
doi = {10.1103/PhysRevA.82.065603},
author = {Francis N. C. Paraan and Vladimir E Korepin}
}
@article {Paraan2009,
title = {Quantum quenches in the Dicke model: Statistics of the work done and of other observables},
journal = {Phys. Rev. E},
volume = {80},
number = {6},
year = {2009},
note = {cited By 14},
pages = {061130},
abstract = {We study the statistics of the work done in a zero temperature quench of the coupling constant in the Dicke model describing the interaction between an ensemble of two level systems and a single bosonic mode. When either the final or the initial coupling constants approach the critical coupling λ_{c} that separates the normal and superradiant phases of the system, the probability distribution of the work done displays singular behavior. The average work tends to diverge as the initial coupling parameter is brought closer to the critical value λ_{c}. In contrast, for quenches ending close to criticality, the distribution of work has finite moments but displays a sequence of edge singularities. This contrasting behavior is related to the difference between the processes of compression and expansion of a particle subject to a sudden change in its confining potential. We confirm this by studying in detail the time-dependent statistics of other observables, such as the quadratures of the photons and the total occupation of the bosonic modes.

},
doi = {10.1103/PhysRevE.80.061130},
author = {Francis N. C. Paraan and Alessandro Silva}
}
@article {Paraan2008,
title = {Brownian motion of a charged particle driven internally by correlated noise},
journal = {Phys. Rev. E},
volume = {77},
number = {2},
year = {2008},
note = {cited By 12},
pages = {022101},
abstract = {We give an exact solution to the generalized Langevin equation of motion of a charged Brownian particle in a uniform magnetic field that is driven internally by an exponentially correlated stochastic force. A strong dissipation regime is described in which the ensemble-averaged fluctuations of the velocity exhibit transient oscillations that arise from memory effects. Also, we calculate generalized diffusion coefficients describing the transport of these particles and briefly discuss how they are affected by the magnetic field strength and correlation time. Our asymptotic results are extended to the general case of internal driving by correlated Gaussian stochastic forces with finite autocorrelation times.

},
doi = {10.1103/PhysRevE.77.022101},
author = {Francis N. C. Paraan and Mikhail P Solon and Jose Perico Esguerra}
}
@article {Paraan2006,
title = {Exact moments in a continuous time random walk with complete memory of its history},
journal = {Phys. Rev. E},
volume = {74},
number = {3},
year = {2006},
note = {cited By 11},
pages = {032101},
abstract = {We present a continuous time generalization of a random walk with complete memory of its history [Phys. Rev. E **70**, 045101(R) (2004)] and derive exact expressions for the first four moments of the distribution of displacement when the number of steps is Poisson distributed. We analyze the asymptotic behavior of the normalized third and fourth cumulants and identify new transitions in a parameter regime where the random walk exhibits superdiffusion. These transitions, which are also present in the discrete time case, arise from the memory of the process and are not reproduced by Fokker-Planck approximations to the evolution equation of this random walk.

},
doi = {10.1103/PhysRevE.74.032101},
author = {Francis N. C. Paraan and Jose Perico Esguerra}
}