Simulations of cold nuclear matter at sub-saturation densities

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Ideal nuclear matter is expected to undergo a first order phase transition at the thermodynamic limit. At such phase transitions the size of density fluctuations (bubbles or droplets) scale with the size of the system. This means that simulations of nuclear matter at sub-saturation densities will in...

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Autores principales:	Giménez Molinelli, P.A., Nichols, J.I., López, J.A., Dorso, C.O.
Formato:	JOUR
Materias:	Finite size effects Molecular dynamics simulations Nuclear astrophysics Nuclear matter phase transition
Acceso en línea:	http://hdl.handle.net/20.500.12110/paper_03759474_v923_n_p31_GimenezMolinelli
Aporte de:	Biblioteca Digital - Facultad de Ciencias Exactas y Naturales (UBA) de Universidad de Buenos Aires

id	todo:paper_03759474_v923_n_p31_GimenezMolinelli
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spelling	todo:paper_03759474_v923_n_p31_GimenezMolinelli2023-10-03T15:30:49Z Simulations of cold nuclear matter at sub-saturation densities Giménez Molinelli, P.A. Nichols, J.I. López, J.A. Dorso, C.O. Finite size effects Molecular dynamics simulations Nuclear astrophysics Nuclear matter phase transition Ideal nuclear matter is expected to undergo a first order phase transition at the thermodynamic limit. At such phase transitions the size of density fluctuations (bubbles or droplets) scale with the size of the system. This means that simulations of nuclear matter at sub-saturation densities will inexorably suffer from what is vaguely referred to as "finite size effects". It is usually thought that these finite size effects can be diminished by imposing periodic boundary conditions and making the system large enough, but as we show in this work, that is actually not the case at sub-saturation densities. In this paper we analyze the equilibrium configurations of molecular dynamics simulations of a classical model for symmetric ideal (uncharged) nuclear matter at sub-saturation densities and low temperatures, where phase coexistence is expected at the thermodynamic limit. We show that the most stable configurations in this density range are almost completely determined by artificial aspects of the simulations (i.e. boundary conditions) and can be predicted analytically by surface minimization. This result is very general and is shown to hold true for several well known semi-classical models of nuclear interaction and even for a simple Lennard-Jones potential. Also, in the limit of very large systems, when "small size" effects can be neglected, those equilibrium configurations seem to be restricted to a few structures reminiscent to the "Pasta Phases" expected in Neutron Star matter, but arising from a completely different origin: In Neutron Star matter, the non-homogeneous structures arise from a competition between nuclear and Coulomb interactions while for ideal nuclear matter they emerge from finite (yet not "small") size effects. The role of periodic boundary conditions and finite size effects in Neutron Star matter simulations are reexamined. © 2014 Elsevier B.V.. Fil:Dorso, C.O. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales; Argentina. JOUR info:eu-repo/semantics/openAccess http://creativecommons.org/licenses/by/2.5/ar http://hdl.handle.net/20.500.12110/paper_03759474_v923_n_p31_GimenezMolinelli
institution	Universidad de Buenos Aires
institution_str	I-28
repository_str	R-134
collection	Biblioteca Digital - Facultad de Ciencias Exactas y Naturales (UBA)
topic	Finite size effects Molecular dynamics simulations Nuclear astrophysics Nuclear matter phase transition
spellingShingle	Finite size effects Molecular dynamics simulations Nuclear astrophysics Nuclear matter phase transition Giménez Molinelli, P.A. Nichols, J.I. López, J.A. Dorso, C.O. Simulations of cold nuclear matter at sub-saturation densities
topic_facet	Finite size effects Molecular dynamics simulations Nuclear astrophysics Nuclear matter phase transition
description	Ideal nuclear matter is expected to undergo a first order phase transition at the thermodynamic limit. At such phase transitions the size of density fluctuations (bubbles or droplets) scale with the size of the system. This means that simulations of nuclear matter at sub-saturation densities will inexorably suffer from what is vaguely referred to as "finite size effects". It is usually thought that these finite size effects can be diminished by imposing periodic boundary conditions and making the system large enough, but as we show in this work, that is actually not the case at sub-saturation densities. In this paper we analyze the equilibrium configurations of molecular dynamics simulations of a classical model for symmetric ideal (uncharged) nuclear matter at sub-saturation densities and low temperatures, where phase coexistence is expected at the thermodynamic limit. We show that the most stable configurations in this density range are almost completely determined by artificial aspects of the simulations (i.e. boundary conditions) and can be predicted analytically by surface minimization. This result is very general and is shown to hold true for several well known semi-classical models of nuclear interaction and even for a simple Lennard-Jones potential. Also, in the limit of very large systems, when "small size" effects can be neglected, those equilibrium configurations seem to be restricted to a few structures reminiscent to the "Pasta Phases" expected in Neutron Star matter, but arising from a completely different origin: In Neutron Star matter, the non-homogeneous structures arise from a competition between nuclear and Coulomb interactions while for ideal nuclear matter they emerge from finite (yet not "small") size effects. The role of periodic boundary conditions and finite size effects in Neutron Star matter simulations are reexamined. © 2014 Elsevier B.V..
format	JOUR
author	Giménez Molinelli, P.A. Nichols, J.I. López, J.A. Dorso, C.O.
author_facet	Giménez Molinelli, P.A. Nichols, J.I. López, J.A. Dorso, C.O.
author_sort	Giménez Molinelli, P.A.
title	Simulations of cold nuclear matter at sub-saturation densities
title_short	Simulations of cold nuclear matter at sub-saturation densities
title_full	Simulations of cold nuclear matter at sub-saturation densities
title_fullStr	Simulations of cold nuclear matter at sub-saturation densities
title_full_unstemmed	Simulations of cold nuclear matter at sub-saturation densities
title_sort	simulations of cold nuclear matter at sub-saturation densities
url	http://hdl.handle.net/20.500.12110/paper_03759474_v923_n_p31_GimenezMolinelli
work_keys_str_mv	AT gimenezmolinellipa simulationsofcoldnuclearmatteratsubsaturationdensities AT nicholsji simulationsofcoldnuclearmatteratsubsaturationdensities AT lopezja simulationsofcoldnuclearmatteratsubsaturationdensities AT dorsoco simulationsofcoldnuclearmatteratsubsaturationdensities
_version_	1807323179923800064

Simulations of cold nuclear matter at sub-saturation densities

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