Nonrelativistic formation of scalar clumps as a candidate for dark matter

We propose a new mechanism for the formation of dark matter clumps in the radiation era. We assume that a light scalar field is decoupled from matter and oscillates harmonically around its vacuum expectation value. We include self-interactions and consider the nonrelativistic regime. The scalar dyna...

Descripción completa

Detalles Bibliográficos
Autores: Brax, Philippe, Valageas, Patrick, Ruiz Cembranos, José Alberto
Tipo de recurso: artículo
Fecha de publicación:2020
País:España
Institución:Universidad Complutense de Madrid (UCM)
Repositorio:Docta Complutense
Idioma:inglés
OAI Identifier:oai:docta.ucm.es:20.500.14352/6705
Acceso en línea:https://hdl.handle.net/20.500.14352/6705
Access Level:acceso abierto
Palabra clave:53
Light
Asymptotics
Constraints
Gap
Física (Física)
22 Física
id ES_db676df07e5ddd33808fe2a7acbce596
oai_identifier_str oai:docta.ucm.es:20.500.14352/6705
network_acronym_str ES
network_name_str España
repository_id_str
spelling Nonrelativistic formation of scalar clumps as a candidate for dark matterBrax, PhilippeValageas, PatrickRuiz Cembranos, José Alberto53LightAsymptoticsConstraintsGapFísica (Física)22 FísicaWe propose a new mechanism for the formation of dark matter clumps in the radiation era. We assume that a light scalar field is decoupled from matter and oscillates harmonically around its vacuum expectation value. We include self-interactions and consider the nonrelativistic regime. The scalar dynamics are described by a fluid approach where the fluid pressure depends on both quantum and self-interaction effects. When the squared speed of sound of the scalar fluid becomes negative, an instability arises and the fluctuations of the scalar energy-density field start growing. They eventually become nonlinear and clumps form. Subsequently, the clumps aggregate and reach a universal regime. Afterwards, they play the role of cold dark matter. We apply this mechanism first to a model with a negative quartic term stabilized by a positive self-interaction of order six, and then to axion monodromy, where a subdominant cosine potential corrects a mass term. In the first case, the squared speed of sound becomes negative when the quartic term dominates, leading to a tachyonic instability. For axion monodromy, the instability starts very slowly after the squared speed of sound first becomes negative and then oscillates around zero. Initially the density perturbations perform acoustic oscillations due to the quantum pressure. Eventually, they start growing exponentially due to a parametric resonance. The shape and the scaling laws of the clumps depend on their formation mechanism. When the tachyonic phase takes place, the core density of the clumps is uniquely determined by the energy density at the beginning of the instability. On the other hand, for axion monodromy, the core density scales with the soliton mass and radius. This difference comes from the crucial role that the quantum pressure plays in both the parametric resonance in the linear regime and in the nonlinear formation regime of static scalar solitons. In both scenarios, the scalar-field clumps span a wide range of scales and masses, running from the size of atoms to that of galactic molecular clouds, and from 10(-3 )gram to thousands of solar masses. Because of finite-size effects, both from the source and the lens, these dark matter clumps are far beyond the reach of microlensing observations. We find that the formation redshift of the scalar clumps can span a large range in the radiation era; the associated background temperature can vary from 10 eV to 10(5) GeV, and the scalar-field mass from 10(-26 )GeV to 10 GeV.Amer Physical SocUniversidad Complutense de Madrid20202020-01-0120202020-01-01journal articlehttp://purl.org/coar/resource_type/c_6501info:eu-repo/semantics/articleapplication/pdfhttps://hdl.handle.net/20.500.14352/6705reponame:Docta Complutenseinstname:Universidad Complutense de Madrid (UCM)Inglésengopen accesshttp://purl.org/coar/access_right/c_abf2info:eu-repo/semantics/openAccessoai:docta.ucm.es:20.500.14352/67052026-06-02T12:44:21Z
dc.title.none.fl_str_mv Nonrelativistic formation of scalar clumps as a candidate for dark matter
title Nonrelativistic formation of scalar clumps as a candidate for dark matter
spellingShingle Nonrelativistic formation of scalar clumps as a candidate for dark matter
Brax, Philippe
53
Light
Asymptotics
Constraints
Gap
Física (Física)
22 Física
title_short Nonrelativistic formation of scalar clumps as a candidate for dark matter
title_full Nonrelativistic formation of scalar clumps as a candidate for dark matter
title_fullStr Nonrelativistic formation of scalar clumps as a candidate for dark matter
title_full_unstemmed Nonrelativistic formation of scalar clumps as a candidate for dark matter
title_sort Nonrelativistic formation of scalar clumps as a candidate for dark matter
dc.creator.none.fl_str_mv Brax, Philippe
Valageas, Patrick
Ruiz Cembranos, José Alberto
author Brax, Philippe
author_facet Brax, Philippe
Valageas, Patrick
Ruiz Cembranos, José Alberto
author_role author
author2 Valageas, Patrick
Ruiz Cembranos, José Alberto
author2_role author
author
dc.contributor.none.fl_str_mv Universidad Complutense de Madrid
dc.subject.none.fl_str_mv 53
Light
Asymptotics
Constraints
Gap
Física (Física)
22 Física
topic 53
Light
Asymptotics
Constraints
Gap
Física (Física)
22 Física
description We propose a new mechanism for the formation of dark matter clumps in the radiation era. We assume that a light scalar field is decoupled from matter and oscillates harmonically around its vacuum expectation value. We include self-interactions and consider the nonrelativistic regime. The scalar dynamics are described by a fluid approach where the fluid pressure depends on both quantum and self-interaction effects. When the squared speed of sound of the scalar fluid becomes negative, an instability arises and the fluctuations of the scalar energy-density field start growing. They eventually become nonlinear and clumps form. Subsequently, the clumps aggregate and reach a universal regime. Afterwards, they play the role of cold dark matter. We apply this mechanism first to a model with a negative quartic term stabilized by a positive self-interaction of order six, and then to axion monodromy, where a subdominant cosine potential corrects a mass term. In the first case, the squared speed of sound becomes negative when the quartic term dominates, leading to a tachyonic instability. For axion monodromy, the instability starts very slowly after the squared speed of sound first becomes negative and then oscillates around zero. Initially the density perturbations perform acoustic oscillations due to the quantum pressure. Eventually, they start growing exponentially due to a parametric resonance. The shape and the scaling laws of the clumps depend on their formation mechanism. When the tachyonic phase takes place, the core density of the clumps is uniquely determined by the energy density at the beginning of the instability. On the other hand, for axion monodromy, the core density scales with the soliton mass and radius. This difference comes from the crucial role that the quantum pressure plays in both the parametric resonance in the linear regime and in the nonlinear formation regime of static scalar solitons. In both scenarios, the scalar-field clumps span a wide range of scales and masses, running from the size of atoms to that of galactic molecular clouds, and from 10(-3 )gram to thousands of solar masses. Because of finite-size effects, both from the source and the lens, these dark matter clumps are far beyond the reach of microlensing observations. We find that the formation redshift of the scalar clumps can span a large range in the radiation era; the associated background temperature can vary from 10 eV to 10(5) GeV, and the scalar-field mass from 10(-26 )GeV to 10 GeV.
publishDate 2020
dc.date.none.fl_str_mv 2020
2020-01-01
2020
2020-01-01
dc.type.none.fl_str_mv journal article
http://purl.org/coar/resource_type/c_6501
dc.type.openaire.fl_str_mv info:eu-repo/semantics/article
format article
dc.identifier.none.fl_str_mv https://hdl.handle.net/20.500.14352/6705
url https://hdl.handle.net/20.500.14352/6705
dc.language.none.fl_str_mv Inglés
eng
language_invalid_str_mv Inglés
language eng
dc.rights.none.fl_str_mv open access
http://purl.org/coar/access_right/c_abf2
dc.rights.openaire.fl_str_mv info:eu-repo/semantics/openAccess
rights_invalid_str_mv open access
http://purl.org/coar/access_right/c_abf2
eu_rights_str_mv openAccess
dc.format.none.fl_str_mv application/pdf
dc.publisher.none.fl_str_mv Amer Physical Soc
publisher.none.fl_str_mv Amer Physical Soc
dc.source.none.fl_str_mv reponame:Docta Complutense
instname:Universidad Complutense de Madrid (UCM)
instname_str Universidad Complutense de Madrid (UCM)
reponame_str Docta Complutense
collection Docta Complutense
repository.name.fl_str_mv
repository.mail.fl_str_mv
_version_ 1869421671887142912
score 15.300724

Similares en LA Referencia