arXiv subjects

C. P. Panos

Publications and source records attributed to C. P. Panos.

At least 19 recordsLinked to original sources

arXiv2023

Configurational entropy as a probe of the stability condition of compact objects

We systematically extend the statement that the configurational entropy provides an alternative approach to studying gravitational stability of compact objects, carried out in the previous work of M. Gleiser and N. Jiang, Phys. Rev. D {\bf 92}, 044046 (2015). Inspired by that paper, we try to answer the crucial question: Is there any one-to-one correspondence between the minimum of the configurational entropy and the stability point for each realistic equation of state? In view of the above question, we focus on neutron stars, quark stars, as well as on the third family of compact stars (hybrid stars), where a possible phase transition may lead to the existence of twin stars (stars with equal mass but different radius). In each case, we use a large set of equations of state investigating the possibility to find correlations between the stability region obtained from the traditional perturbation methods to the one obtained by the minimum of configurational entropy. We found that the suggested prediction of the stability by the minimization of the configurational entropy, concerning neutron stars and quark stars, does not have, at least quantitatively, universal validity. However, in several cases it qualitatively predicts the existence of the stability point. In conclusion, the configurational entropy, can be considered as an additional tool which enters into the quiver for studying the stability of compact objects such as for example neutron and quark stars, but taking into account that the accuracy of the predictions depends on the specific character of each equation of state.

gr-qc↗

arXiv2019

A simple link of information entropy of quantum and classical systems with Newtonian $r^{-2}$ dependence of Verlinde's entropic force

It is shown that the entropic force formula $F_e=-λ\partial S/\partial A$ leads to a Newtonian $r^{-2}$ dependence. Here we employ the universal property of the information entropy $S=a+b\ln N$ ($N$ is the number of particles of a quantum system and $A$ is the area containing the system). This property was previously obtained for fermionic systems (atoms, atomic clusters, nuclei and infinite Fermi systems i.e. electron gas, liquid $^3$He and nuclear matter) and bosonic ones (correlated boson-atoms in a trap). A similar dependence of the entropic force has been derived very recently by Plastino et al with a Bose or Fermi gas entropy, inspired by Verlinde's conjecture~\cite{Verlide-11} that gravity is an emergent entropic force. Finally, we point out that our simple argument holds for classical systems as well.

quant-ph↗

arXiv2018

Information and complexity measures in the interface of a metal and a superconductor

Fisher information, Shannon information entropy and Statistical Complexity are calculated for the interface of a normal metal and a superconductor, as a function of the temperature for several materials. The order parameter $Ψ({\bf r})$ derived from the Ginzburg-Landau theory is used as an input together with experimental values of critical transition temperature $T_c$ and the superconducting coherence length $ξ_0$. Analytical expressions are obtained for information and complexity measures. Thus $T_c$ is directly related in a simple way with disorder and complexity. An analytical relation is found of the Fisher Information with the energy profile of superconductivity i.e. the ratio of surface free energy and the bulk free energy. We verify that a simple relation holds between Shannon and Fisher information i.e. a decomposition of a global information quantity (Shannon) in terms of two local ones (Fisher information), previously derived and verified for atoms and molecules by Liu et al. Finally, we find analytical expressions for generalized information measures like the Tsallis entropy and Fisher information. We conclude that the proper value of the non-extensivity parameter $q\simeq 1$, in agreement with previous work using a different model, where $q\simeq 1.005$.

quant-ph↗

arXiv2013

Fisher Information and Atomic Structure

We present a comparative study of several information and statistical complexity measures in order to examine a possible correlation with certain experimental properties of atomic structure. Comparisons are also carried out quantitatively using Pearson correlation coefficient. In particular, we show that Fisher information in momentum space is very sensitive to shell effects, and is directly associated with some of the most characteristic atomic properties, such as atomic radius, ionization energy, electronegativity, and atomic dipole polarizability. Finally we present a relation that emerges between Fisher information and the second moment of the probability distribution in momentum space i.e. an energy functional of interest in (e,2e) experiments.

quant-ph↗

arXiv2013

Quantum Tunneling and Information Entropy in a Double Square Well Potential: Ammonia Molecule

Quantum tunneling is the quantum-mechanical effect where a particle tunnels through a classically forbidden region. Double Square Well Potential (DSWP) is a system where this phenomenon is feasible. Numerous phenomena can be illustrated by considering motion in a pair of wells that are separated by a barrier of finite height and width. The energy level splitting, resulting from barrier penetration, is the reason of the so-called inversion spectrum, which is an example of quantum tunneling. Out of several molecules ($NH_3$, $PH_3$, $AsH_3$, $NH_2CN$) where this inversion phenomenon occurs, ammonia molecule $NH_3$ provides a nice physical realization of a vibrational system with a DSWP. The main goal of the present work is to examine the implications of quantum tunneling on information entropy measures (Shannon's and Fisher's) and statistical complexity.

quant-ph↗

arXiv2010

Statistical measure of complexity of hard-sphere gas: applications to nuclear matter

We apply the statistical measure of complexity, introduced by López-Ruiz, Mancini and Calbet to a hard-sphere dilute Fermi gas whose particles interact via a repulsive hard-core potential. We employ the momentum distribution of this system to calculate the information entropy, the disequilibrium and the statistical complexity. We examine possible connections between the particle correlations and energy of the system with those information and complexity measures. The hard-sphere model serves as a test bed for concepts about complexity.

quant-ph↗

arXiv2009

Statistical measure of complexity and correlated behavior of Fermi systems

We apply the statistical measure of complexity, introduced by López-Ruiz, Mancini and Calbet (LMC), to uniform Fermi systems. We investigate the connection between information and complexity measures with the strongly correlated behavior of various Fermi systems as nuclear matter, electron gas and liquid helium. We examine the possibility that LMC complexity can serve as an index quantifying correlations in the specific system and to which extent could be related with experimental quantities. Moreover, we concentrate on thermal effects on the complexity of ideal Fermi systems. We find that complexity behaves, both at low and high values of temperature, in a similar way as the specific heat.

cond-mat.stat-mech↗

arXiv2009

Complexity and neutron stars structure

We apply the statistical measure of complexity introduced by Lopez-Ruiz, Mancini and Calbet to neutron stars structure. Neutron stars is a classical example where the gravitational field and quantum behavior are combined and produce a macroscopic dense object. Actually, we continue the recent application of Sanudo and Pacheco to white dwarfs structure. We concentrate our study on the connection between complexity and neutron star properties, like maximum mass and the corresponding radius, applying a specific set of realistic equation of states. Moreover, the effect of the strength of the gravitational field on the neutron star structure and consequently on the complexity measure is also investigated. It is seen that neutron stars, consistent with astronomical observations so far, are ordered systems (low complexity), which cannot grow in complexity as their mass increases. This is a result of the interplay of gravity, the short-range nuclear force and the very short-range weak interaction.

astro-ph.SR↗

arXiv2009

Equation of state for $β$-stable hot nuclear matter

We provide an equation of state for hot nuclear matter in $β$-equilibrium by applying a momentum-dependent effective interaction. We focus on the study of the equation of state of high-density and high-temperature nuclear matter, containing leptons (electrons and muons) under the chemical equilibrium condition in which neutrinos have left the system. The conditions of charge neutrality and equilibrium under $β$-decay process lead first to the evaluation of proton and lepton fractions and afterwards of internal energy, free energy, pressure and in total to the equation of state of hot nuclear matter. Thermal effects on the properties and equation of state of nuclear matter are assesed and analyzed in the framework of the proposed effective interaction model. Special attention is dedicated to the study of the contribution of the components of $β$-stable nuclear matter to the entropy per particle, a quantity of great interest for the study of structure and collapse of supernova.

nucl-th↗

arXiv2009

Complexity classification of quantum many-body systems according to the Pair of Order-Disorder Indices (PODI)

The statistical measures of complexity defined by Lopez-Ruiz, Mancini, and Calbet (LMC) and Shiner, Davison and Landsberg (SDL) are calculated as functions of the number of particles for four quantum many-body systems, i.e. atoms, nuclei, atomic clusters, and correlated atoms in a trap (bosons). A pair of order and disorder strengths, evaluated for each system, can serve as a Pair of Order-Disorder Indices (PODI), characterizing quantitatively order versus disorder in any quantum system. According to the above classification, we assign to bosons the complexity character of disorder, to atoms the character of order, while nuclei and atomic clusters are (less) disordered and lie between them. This criterion can be used to estimate the relative contribution of order and disorder to complexity for other more complicated quantum systems as well and even classical ones, if one is able to describe them probabilistically. We also address the issue, whether those systems can grow in complexity as the number of particles increases. Our comparative study indicates that atoms are the only quantum system out of four, which is ordered, with the ability to self-organize. We conjecture that this is an information-theoretic reason that atoms are suitable as building blocks of larger structures of biological interest i.e. molecules and macromolecules. This is in the spirit of Wheeler's "it from bit" quote, the project to present everything about the Universe in terms of information theory.

quant-ph↗

arXiv2008

A simple method for the evaluation of the information content and complexity in atoms. A proposal for scalability

We present a very simple method for the calculation of Shannon, Fisher, Onicescu and Tsallis entropies in atoms, as well as SDL and LMC complexity measures, as functions of the atomic number Z. Fractional occupation probabilities of electrons in atomic orbitals are employed, instead of the more complicated continuous electron probability densities in position and momentum spaces, used so far in the literature. Our main conclusions are compatible with the results of more sophisticated approaches and correlate fairly with experimental data. We obtain for the Tsallis entropic index the value q=1.031, which shows that atoms are very close to extensivity. A practical way towards scalability of the quantification of complexity for systems with more components than the atom is indicated. We also discuss the issue if the complexity of the electronic structure of atoms increases with Z. A Pair of Order-Disorder Indices (PODI), which can be introduced for any quantum many-body system, is evaluated in atoms. We conclude that "atoms are ordered systems, which do not grow in complexity as Z increases".

quant-ph↗

arXiv2007

Application of information and complexity theories to public opinion polls. The case of Greece (2004-2007)

A general methodology to study public opinion inspired from information and complexity theories is outlined. It is based on probabilistic data extracted from opinion polls. It gives a quantitative information-theoretic explanation of high job approval of Greek Prime Minister Mr. Constantinos Karamanlis (2004-2007), while the same time series of polls conducted by the company Metron Analysis showed that his party New Democracy (abbr. ND) was slightly higher than the opposition party of PASOK -party leader Mr. George Papandreou. It is seen that the same mathematical model applies to the case of the popularity of President Clinton between January 1998 and February 1999, according to a previous study, although the present work extends the investigation to concepts as complexity and Fisher information, quantifying the organization of public opinion data.

stat.AP↗

arXiv2006

Comparison of SDL and LMC measures of complexity: Atoms as a testbed

The "simple" measure of complexity of Shiner, Davison and Landsberg (SDL) and the "statistical" one, according to Lopez-Ruiz, Mancini and Calbet (LMC), are compared in atoms as functions of the atomic number Z. Shell effects i.e. local minima at the closed shells atoms are observed, as well as certain qualitative trends of SDL and LMC measueres of complexity. If we impose the condition that SDL and LMC behave similarly as functions of Z, then we can conclude that complexity increases with Z and for atoms the strength of disorder is zero and order is four.

quant-ph↗

arXiv2006

Net Fisher information measure versus ionization potential and dipole polarizability in atoms

The net Fisher information measure, defined as the product of position and momentum Fisher information measures and derived from the non-relativistic Hartree-Fock wave functions for atoms with Z=1-102, is found to correlate well with the inverse of the experimental ionization potential. Strong direct correlations of the net Fisher information are also reported for the static dipole polarizability of atoms with Z=1-88. The complexity measure, defined as the ratio of the net Onicescu information measure and net Fisher information, exhibits clearly marked regions corresponding to the periodicity of the atomic shell structure. The reported correlations highlight the need for using the net information measures in addition to either the position or momentum space analogues. With reference to the correlation of the experimental properties considered here, the net Fisher information measure is found to be superior than the net Shannon information entropy.

quant-ph↗

arXiv2006

Quantum Computation Beyond the "Standard Circuit Model"

Construction of explicit quantum circuits follows the notion of the "standard circuit model" introduced in the solid and profound analysis of elementary gates providing quantum computation. Nevertheless the model is not always optimal (e.g. concerning the number of computational steps) and it neglects physical systems which cannot follow the "standard circuit model" analysis. We propose a computational scheme which overcomes the notion of the transposition from classical circuits providing a computation scheme with the least possible number of Hamiltonians in order to minimize the physical resources needed to perform quantum computation and to succeed a minimization of the computational procedure (minimizing the number of computational steps needed to perform an arbitrary unitary transformation). It is a general scheme of construction, independent of the specific system used for the implementation of the quantum computer. The open problem of controllability in Lie groups is directly related and rises to prominence in an effort to perform universal quantum computation.

quant-ph↗

arXiv2006

Applications of density matrices in a trapped Bose gas

An overview of the Bose-Einstein condensation of correlated atoms in a trap is presented by examining the effect of interparticle correlations to one- and two-body properties of the above systems at zero temperature in the framework of the lowest order cluster expansion. Analytical expressions for the one- and two-body properties of the Bose gas are derived using Jastrow-type correlation function. In addition numerical calculations of the natural orbitals and natural occupation numbers are also carried out. Special effort is devoted for the calculation of various quantum information properties including Shannon entropy, Onicescu informational energy, Kullback-Leibler relative entropy and the recently proposed Jensen-Shannon divergence entropy. The above quantities are calculated for the trapped Bose gases by comparing the correlated and uncorrelated cases as a function of the strength of the short-range correlations. The Gross-Piatevskii equation is solved giving the density distributions in position and momentum space, which are employed to calculate quantum information properties of the Bose gas.

cond-mat.other↗

arXiv2005

Information Entropy, Information Distances and Complexity in Atoms

Shannon information entropies in position and momentum spaces and their sum are calculated as functions of Z (Z=2-54) in atoms. Roothaan-Hartree-Fock electron wave functions are used. The universal property S=a+b lnZ is verified. In addition, we calculate the Kullback-Leibler relative entropy, the Jensen-Shannon divergence, Onicescu's information energy and a complexity measure recently proposed. Shell effects at closed shells atoms are observed. The complexity measure shows local minima at the closed shells atoms indicating that for the above atoms complexity decreases with respect to neighboring atoms. It is seen that complexity fluctuates around an average value, indicating that the atom cannot grow in complexity as Z increases. Onicescu's information energy is correlated with the ionization potential. Kullback distance and Jensen-Shannon distance are employed to compare Roothaan-Hartree-Fock density distributions with other densities of previous works.

quant-ph↗

arXiv2005

Quantum-Information Content of Fractional Occupation Probabilities in Nuclei

Three measures of the information content of a probability distribution are briefly reviewed. They are applied to fractional occupation probabilities in light nuclei, taking into account short-range correlations. The effect of short-range correlations is to increase the information entropy (or disorder) of nuclei, comparing with the independent particle model. It is also indicated that the information entropy can serve as a sensitive index of order and short-range correlations in nuclei. It is concluded that increasing $Z$, the information entropy increases i.e. the disorder of the nucleus increases for all measures of information considered in the present work.

quant-ph↗