Search

We consider the phase shift in the gravitational wave signal induced by fast oscillations of scalar dark matter surrounding binary systems, which could be probed by the future experiments LISA and DECIGO. This effect depends on the local matter density and the mass of the dark matter particle. We compare it to the phase shift due to a standard dynamical friction term, which should generically be present. We find that the effect associated with the oscillations only dominates over the dynamical friction for dark matter masses below 10-21 eV, with masses below 10-23 eV implying cloud sizes that are too large to be realistic. Moreover, for masses of the order of 10-21 eV, LISA and DECIGO would only detect this effect for dark matter densities greater than that in the solar system by a factor 105 or 104 respectively. We conclude that this signal can be ignored for most dark matter scenarios unless very dense clouds of very light dark matter are created early in the Universe at a redshift z similar to 104., Ministerio de Ciencia e Innovación (España), European Commission, Université Paris-Saclay, P2IO Laboratory of Excellence, Agence Nationale de la Recherche (France), Science and Technology Facilities Council (UK), Depto. de Física Teórica, Fac. de Ciencias Físicas, Instituto de Física de Partículas y del Cosmos (IPARCOS), TRUE, pub, CA21106, CA21136, ANR-11-IDEX-0003-01, ANR-10-LABX-0038, ST/ T000732/1.

2023 Descuento SCOAP, We provide a reinterpretation of the quantum vacuum ambiguities that one encounters when studying particle creation phenomena due to an external and time-dependent agent. We propose a measurement-motivated understanding: Each way of measuring the number of created particles selects a particular vacuum. This point of view gives a clear and physical meaning to the time evolution of the number of particles produced by the agent as the counts in a specific detector and, at the same time, relates commonly used quantization prescriptions to particular measurement setups., Ministerio de Ciencia e Innovación (España), Agencia Estatal de Investigación (España), Fondo Europeo de Desarrollo Regional (FEDER), European Commission, European Cooperation in Science and Technology, Ministerio de Universidades (España), Centro de Excelencia Severo Ochoa (España), Depto. de Física Teórica, Fac. de Ciencias Físicas, Instituto de Física de Partículas y del Cosmos (IPARCOS), TRUE, pub, Descuento UCM

2023 Descuento SCOAP, We provide a reinterpretation of the quantum vacuum ambiguities that one encounters when studying particle creation phenomena due to an external and time-dependent agent. We propose a measurement-motivated understanding: Each way of measuring the number of created particles selects a particular vacuum. This point of view gives a clear and physical meaning to the time evolution of the number of particles produced by the agent as the counts in a specific detector and, at the same time, relates commonly used quantization prescriptions to particular measurement setups., Ministerio de Ciencia e Innovación (España), Agencia Estatal de Investigación (España), Fondo Europeo de Desarrollo Regional (FEDER), European Commission, European Cooperation in Science and Technology, Ministerio de Universidades (España), Centro de Excelencia Severo Ochoa (España), Depto. de Física Teórica, Fac. de Ciencias Físicas, Instituto de Física de Partículas y del Cosmos (IPARCOS), TRUE, pub, Descuento UCM

©2003 The American Physical Society, We consider a general brane-world model parametrized by the brane tension scale f and the branon mass M. For a low tension compared to the fundamental gravitational scale, we calculate the relic branon abundance and its contribution to the cosmological dark matter. We compare this result with the current observational limits on the total and hot dark matter energy densities and derive the corresponding bounds on f and M. Using the nucleosynthesis bounds on the number of relativistic species, we also set a limit on the number of light branons in terms of the brane tension. Finally, we estimate the bounds coming from the energy loss rate in supernovae explosions due to massive branon emission., Depto. de Física Teórica, Fac. de Ciencias Físicas, TRUE, pub

© 2014 American Physical Society. This work has been supported by MICINN (Spain) Projects No. FIS2011-23000, No. FPA2011-27853-01 and Consolider-Ingenio MULTIDARK No. CSD2009- 00064. F. D. A. acknowledges financial support from the UAM+CSIC Campus of International Excellence (Spain) and the kind hospitality of the Instituto de Astrofísica de Canarias (IAC) while writing the manuscript., We consider the vacuum energy of massive quantum fields in an expanding universe. We define a conserved renormalized energy-momentum tensor by means of a comoving cutoff regularization. Using exact solutions for de Sitter space-time, we show that in a certain range of mass and renormalization scales there is a contribution to the vacuum energy density that scales as nonrelativistic matter and that such a contribution becomes dominant at late times. By means of the WKB approximation, we find that these results can be extended to arbitrary Robertson-Walker geometries. We study the range of parameters in which the vacuum energy density would be compatible with current limits on dark matter abundance. Finally, by calculating the vacuum energy in a perturbed Robertson-Walker background, we obtain the speed of sound of density perturbations and show that the vacuum energy density contrast can grow on sub-Hubble scales as in standard cold dark matter scenarios., MICINN (Spain), Consolider-Ingenio MULTIDARK, CSD2009- 00064, UAM+CSIC Campus of International Excellence (Spain), Depto. de Física Teórica, Fac. de Ciencias Físicas, TRUE, pub

© 2006 The American Physical Society. This work is partially supported by DGICYT (Spain) under project numbers FPA 2004-02602 and BFM 2002- 01003, by NSF grant No. PHY-0239817 and by the Fulbright-MEC (Spain) program., We study the possibility to explain the nonbaryonic dark matter abundance and improve the present fits on the muon anomalous magnetic moment through the same new physics. In this work we show that massive brane fluctuations (branons) in large extra-dimensions models can provide an economical way to deal with these two issues. This is so because the low-energy branon physics depends effectively on essentially only three parameters. Next collider experiments, such as LHC or ILC, will be sensitive to branon phenomenology in the natural parameter region where the theory is able to account for the two effects., DGICYT (Spain), NSF grant, Fulbright-MEC (Spain), Depto. de Física Teórica, Fac. de Ciencias Físicas, TRUE, pub

© 2003 The American Physical Society. This work has been partially supported by the DGICYT (Spain) under Projects No. FPA 2000-0956 and No. BFM2000-1326., We show that, in the context of brane-world scenarios with low tension [tau]=f^4, massive brane fluctuations (branons) are natural dark matter candidates. We calculate the present abundances for both hot (warm) and cold branons in terms of the branon mass M and the tension scale f. The results are compared with the current experimental bounds on these parameters. We also study the prospects for their detection in direct search experiments and comment on their characteristic signals in the indirect ones., DGICYT (Spain), Depto. de Física Teórica, Fac. de Ciencias Físicas, TRUE, pub

© 2013 American Physical Society. The authors thankfully acknowledge the computer resources, technical expertise, and assistance provided by the Barcelona Supercomputing Centre—Centro Nacional de Supercomputación—and the Tirant supercomputer support staff at Valencia. We are also pleased to thank Professor Antonio L. Maroto and Professor Torbjo¨rn Sjöstrand for their useful help and comments. This work has been supported by MICINN (Spain) Project Nos. FIS 2008-01323, FIS2011-23000, and FPA2011-27853-01 and Consolider-Ingenio MULTIDARK CSD2009-00064. R. L.D. is a fellow of FPI, Ref. BES-2012-056054., We explore the viscosities of a photon gas by means of the Euler-Heisenberg effective theory and quantum electrodynamics at zero electron chemical potential. We find parametric estimates that show a very large shear viscosity and an extremely small bulk viscosity (reflecting the very weak coupling simultaneously with a very approximate dilatation invariance). The system is of some interest because it exemplifies very neatly the influence of the breaking of scale invariance on the bulk viscosity., MICINN (Spain), Consolider-Ingenio MULTIDARK, Depto. de Física Teórica, Fac. de Ciencias Físicas, TRUE, pub

© 2012 American Physical Society. We would like to thank Daniel Nieto for useful comments. This work has been supported by Ministerio de Ciencia y Innovación (Spain) project numbers FIS 2008- 01323, FPA 2008-00592, and Consolider-Ingenio Multimessenger Approach for Dark Matter Detection (MULTIDARK) CSD2009-00064. A. d. l. C.-D. also acknowledges the University Research Council, the National Research Foundation (South Africa), and Universidad Complutense de Madrid., Branons are new degrees of freedom that appear in flexible brane-world models corresponding to brane fluctuations. These new fields can behave as standard weakly interacting massive particles (WIMPs) with a significant associated thermal relic density. We analyze the present constraints from their spontaneous annihilations into photons for Energetic Gamma-Ray Experiment Telescope (EGRET), Fermi Large Area Telescope (LAT), and Major Atmospheric Gamma-Ray Imaging Cherenkov (MAGIC) telescopes, and the prospects for detection in future Cherenkov telescopes. In particular, we focus on possible signals coming from the Galactic center and different dwarf spheroidals, such as Draco, Sagittarius, Canis Major and SEGUE 1. We conclude that for those targets, present observations are below the sensitivity limits for branon detection by assuming standard dark matter distributions and no additional boost factors. However, future experiments such as the Cherenkov Telescope Array (CTA) could be able to detect gamma-ray photons coming from the annihilation of branons with masses higher than 150 GeV., Ministerio de Ciencia e Innovacion, Spain, Consolider-Ingenio Multimessenger Approach for Dark Matter Detection (MULTIDARK), Depto. de Física Teórica, Fac. de Ciencias Físicas, TRUE, pub

© 2012 American Physical Society. This work has been supported by MICINN (Spain) Projects No. FIS 2008-01323, No. FIS2011-23000, No. FPA2011-27853-01 and Consolider-Ingenio MULTIDARK CSD2009-00064. J.A.R. C. acknowledges the kind hospitality of the Institute of Theoretical Astrophysics at the University of Oslo, Norway, We show that the gamma ray spectrum observed with the HESS array of Cherenkov telescopes coming from the Galactic Center region and identified with the source HESS J1745-290 is well fitted by the secondary photons coming from dark matter (DM) annihilation over a diffuse power law background. The amount of photons and morphology of the signal localized within a region of few parsecs, require compressed DM profiles as those resulting from baryonic contraction, which offer 103 enhancements in the signal over DM alone simulations. The fitted background from HESS data is consistent with recent Fermi-LAT observations of the same region., MICINN (Spain), Depto. de Física Teórica, Fac. de Ciencias Físicas, TRUE, pub

© 2004 The American Physical Society. We would like to thank J. Terrón, M. Vázquez, and M. Spiropulu for useful comments and experimental information. This work has been partially supported by the DGICYT (Spain) under Projects No. FPA2000-0956 and No. BFM2002-01003., In the context of the brane-world scenarios with compactified extra dimensions, we study the production of brane fluctuations (branons) in hadron colliders (p (p) over bar, pp, and e(+/-)p) in terms of the brane tension parameter f, the branon mass M, and the number of branons N. From the absence of monojet events at HERA and Tevatron (run I), we set bounds on these parameters and we also study how such bounds could be improved at Tevatron (run II) and the future LHC. The single-photon channel is also analyzed for the two last colliders., DGICYT (Spain), Depto. de Física Teórica, Fac. de Ciencias Físicas, TRUE, pub

© 2013 American Physical Society. J. A. R. C. and A. d. l. C. D. acknowledge financial support from MINECO (Spain) Projects No. FIS2011-23000, No. FPA2011-27853-C02-01 and Consolider-Ingenio MULTIDARK CSD2009-00064. A. d. l. C. D. also acknowledges financial support from Marie Curie-Beatriu de Pinos Contract No. BP-B00195, Generalitat de Catalunya and ACGC, University of Cape Town. L. O. G. is indebted to the Theoretical Physics Department, Complutense University of Madrid for the use of technical resources. A. d. l. C. D acknowledges the hospitality of Kavli Institute for Theoretical Physics China (KITPC), Chinese Academy of Sciences, during the last stages of this manuscript., In the context of scalar-tensor theories we study the evolution of the density contrast for Jordan-Fierz-Brans-Dicke theories in a Friedmann-Lemaitre-Robertson-Walker universe. Calculations are performed in the Einstein frame with the cosmological background described as Lambda-cold dark matter (Lambda CDM) and supplemented by a Jordan-Fierz-Brans-Dicke field. By using a completely general procedure valid for all scalar-tensor theories, we obtain the exact fourth-order differential equation for the density contrast evolution in modes of arbitrary size. In the case of sub-Hubble modes, the expression reduces to a simpler but still fourth-order equation that is then compared with the standard (quasistatic) approximation. Differences with respect to the evolution as predicted by the standard concordance Lambda CDM model are observed depending on the value of the coupling., Ministerio de Economía y Competitividad (MINECO), Actividad Investigadora CONSOLIDER - INGENIO - MULTIDARK (MINECO), Acciones Marie Skłodowska-Curie (UE), Generalitat de Catalunya, ACGC, University of Cape Town, Programa Beatriu de Pinós (BP-DGR), Unión Europea (UE), Depto. de Física Teórica, Fac. de Ciencias Físicas, TRUE, pub

© 2012 American Physical Society. This work has been supported by MICINN (Spain) under Project Nos. FIS 2008-01323, FIS2011-23000, FPA2011- 27853 01 and Consolider-Ingenio MULTIDARK under Contract No. CSD2009-00064., We consider homogeneous Abelian vector fields in an expanding universe. We find a mechanical analogy in which the system behaves as a particle moving in three dimensions under the action of a central potential. In the case of bounded and rapid evolution compared to the rate of expansion, we show-by making use of the virial theorem-that for an arbitrary potential and polarization pattern, the average energy-momentum tensor is always diagonal and isotropic despite the intrinsic anisotropic evolution of the vector field. For simple power law potentials of the form V = lambda(A(mu)A(mu))(n), the average equation of state is found to be w = (n - 1)/(n + 1). This implies that vector coherent oscillations could act as natural dark matter or dark energy candidates. Finally, we show that under very general conditions, the average energy-momentum tensor of a rapidly evolving bounded vector field in any background geometry is always isotropic and has the perfect fluid form for any locally inertial observer., MICINN (Spain), Depto. de Física Teórica, Fac. de Ciencias Físicas, TRUE, pub

© 2013 American Physical Society. We thank Marco Peloso and Jose Beltrán Jiménez for useful comments. This work has been supported by MICINN (Spain) project numbers FIS2011-23000, FPA2011-27853-01, and Consolider-Ingenio MULTIDARK CSD2009-00064., We consider homogeneous non-Abelian vector fields with general potential terms in an expanding universe. We find a mechanical analogy with a system of N interacting particles (with N the dimension of the gauge group) moving in three dimensions under the action of a central potential. In the case of bounded and rapid evolution compared to the rate of expansion, we show by making use of a generalization of the virial theorem that for an arbitrary potential and polarization pattern, the average energy-momentum tensor is always diagonal and isotropic despite the intrinsic anisotropic evolution of the vector field. We consider also the case in which a gauge-fixing term is introduced in the action and show that the average equation of state does not depend on such a term. Finally, we extend the results to arbitrary background geometries and show that the average energy-momentum tensor of a rapidly evolving Yang-Mills field is always isotropic and has the perfect fluid form for any locally inertial observer., MICINN (Spain), Depto. de Física Teórica, Fac. de Ciencias Físicas, TRUE, pub

©2001 The American Physical Society. This work was partially supported by the Ministerio de Educación y Ciencia (Spain) (CICYT AEN 97-1693 and PB98-0782), In the context of a brane world and including an induced curvature term in the brane action, we obtain the effective Lagrangian for the Goldstone bosons (branons) associated with the spontaneous breaking of the translational invariance in the bulk. In addition to the branons, this effective action has Skyrmion-like solitonic states which can be understood as holes in the brane. We study their main properties such as mass and size, the Skyrmion-branon interaction, and their possible fermionic quantization. We also consider states where the brane is wrapped around the extra dimensions and their relation with the brane-Skyrmions. Finally, we extend our results to higher-dimensional branes, such as those appearing in M theory, where brane-Skyrmions could also be present., Ministerio de Educación y Ciencia (Spain), Depto. de Física Teórica, Fac. de Ciencias Físicas, TRUE, pub

© 2014 American Physical Society. We would like to thank Juande Zornoza and Carlos de los Heros for useful comments. This work has been supported by UCM predoctoral grant, MICINN (Spain) project numbers FIS 2008-01323, FIS2011-23000, FPA2011-27853-01, Consolider-Ingenio MULTIDARK CSD2009-00064, and the Department of Energy, Contract DE-AC02-76SF00515. J. A. R. C. thanks the support of the Becas Complutense del Amo program., The spectral study of the HESS J1745-290 high-energy gamma-ray cutoff from the Galactic center is compatible with a signal of dark matter (DM) annihilation or decay. If this is the case, a neutrino flux from that source is also expected. We analyze the neutrino flux predicted by DM particles able to create the HESS J1745-290 gamma-rays observations. We focus on the electroweak and hadronic channels, which are favored by present measurements. In particular, we study DM annihilating into W+W- and u (u) over bar with DM masses of 48.8 and 27.9 TeV, respectively. We estimate the resolution angle and exposition time necessary to test the DM hypothesis as the origin of the gamma-ray signal., MICINN (Spain), Consolider-Ingenio MULTIDARK, Department of Energy, Depto. de Física Teórica, Fac. de Ciencias Físicas, TRUE, pub

© 2014 American Physical Society. This work has been supported by MICINN (Spain) Projects No. FIS2011-23000, No. FPA2011-27853-01 and Consolider-Ingenio MULTIDARK No. CSD2009- 00064. F. D. A. acknowledges financial support from the UAM+CSIC Campus of International Excellence (Spain) and the kind hospitality of the Instituto de Astrofísica de Canarias (IAC) while writing the manuscript., We consider the vacuum energy of massive quantum fields in an expanding universe. We define a conserved renormalized energy-momentum tensor by means of a comoving cutoff regularization. Using exact solutions for de Sitter space-time, we show that in a certain range of mass and renormalization scales there is a contribution to the vacuum energy density that scales as nonrelativistic matter and that such a contribution becomes dominant at late times. By means of the WKB approximation, we find that these results can be extended to arbitrary Robertson-Walker geometries. We study the range of parameters in which the vacuum energy density would be compatible with current limits on dark matter abundance. Finally, by calculating the vacuum energy in a perturbed Robertson-Walker background, we obtain the speed of sound of density perturbations and show that the vacuum energy density contrast can grow on sub-Hubble scales as in standard cold dark matter scenarios., MICINN (Spain), Consolider-Ingenio MULTIDARK, CSD2009- 00064, UAM+CSIC Campus of International Excellence (Spain), Depto. de Física Teórica, Fac. de Ciencias Físicas, TRUE, pub

© 2014 American Physical Society. We would like to thank Juande Zornoza and Carlos de los Heros for useful comments. This work has been supported by UCM predoctoral grant, MICINN (Spain) project numbers FIS 2008-01323, FIS2011-23000, FPA2011-27853-01, Consolider-Ingenio MULTIDARK CSD2009-00064, and the Department of Energy, Contract DE-AC02-76SF00515. J. A. R. C. thanks the support of the Becas Complutense del Amo program., The spectral study of the HESS J1745-290 high-energy gamma-ray cutoff from the Galactic center is compatible with a signal of dark matter (DM) annihilation or decay. If this is the case, a neutrino flux from that source is also expected. We analyze the neutrino flux predicted by DM particles able to create the HESS J1745-290 gamma-rays observations. We focus on the electroweak and hadronic channels, which are favored by present measurements. In particular, we study DM annihilating into W+W- and u (u) over bar with DM masses of 48.8 and 27.9 TeV, respectively. We estimate the resolution angle and exposition time necessary to test the DM hypothesis as the origin of the gamma-ray signal., MICINN (Spain), Consolider-Ingenio MULTIDARK, Department of Energy, Depto. de Física Teórica, Fac. de Ciencias Físicas, TRUE, pub

© 2013 American Physical Society. The authors thankfully acknowledge the computer resources, technical expertise, and assistance provided by the Barcelona Supercomputing Centre—Centro Nacional de Supercomputación—and the Tirant supercomputer support staff at Valencia. We are also pleased to thank Professor Antonio L. Maroto and Professor Torbjo¨rn Sjöstrand for their useful help and comments. This work has been supported by MICINN (Spain) Project Nos. FIS 2008-01323, FIS2011-23000, and FPA2011-27853-01 and Consolider-Ingenio MULTIDARK CSD2009-00064. R. L.D. is a fellow of FPI, Ref. BES-2012-056054., We explore the viscosities of a photon gas by means of the Euler-Heisenberg effective theory and quantum electrodynamics at zero electron chemical potential. We find parametric estimates that show a very large shear viscosity and an extremely small bulk viscosity (reflecting the very weak coupling simultaneously with a very approximate dilatation invariance). The system is of some interest because it exemplifies very neatly the influence of the breaking of scale invariance on the bulk viscosity., MICINN (Spain), Consolider-Ingenio MULTIDARK, Depto. de Física Teórica, Fac. de Ciencias Físicas, TRUE, pub

© 2013 American Physical Society. We thank Marco Peloso and Jose Beltrán Jiménez for useful comments. This work has been supported by MICINN (Spain) project numbers FIS2011-23000, FPA2011-27853-01, and Consolider-Ingenio MULTIDARK CSD2009-00064., We consider homogeneous non-Abelian vector fields with general potential terms in an expanding universe. We find a mechanical analogy with a system of N interacting particles (with N the dimension of the gauge group) moving in three dimensions under the action of a central potential. In the case of bounded and rapid evolution compared to the rate of expansion, we show by making use of a generalization of the virial theorem that for an arbitrary potential and polarization pattern, the average energy-momentum tensor is always diagonal and isotropic despite the intrinsic anisotropic evolution of the vector field. We consider also the case in which a gauge-fixing term is introduced in the action and show that the average equation of state does not depend on such a term. Finally, we extend the results to arbitrary background geometries and show that the average energy-momentum tensor of a rapidly evolving Yang-Mills field is always isotropic and has the perfect fluid form for any locally inertial observer., MICINN (Spain), Depto. de Física Teórica, Fac. de Ciencias Físicas, TRUE, pub

© 2013 American Physical Society. J. A. R. C. and A. d. l. C. D. acknowledge financial support from MINECO (Spain) Projects No. FIS2011-23000, No. FPA2011-27853-C02-01 and Consolider-Ingenio MULTIDARK CSD2009-00064. A. d. l. C. D. also acknowledges financial support from Marie Curie-Beatriu de Pinos Contract No. BP-B00195, Generalitat de Catalunya and ACGC, University of Cape Town. L. O. G. is indebted to the Theoretical Physics Department, Complutense University of Madrid for the use of technical resources. A. d. l. C. D acknowledges the hospitality of Kavli Institute for Theoretical Physics China (KITPC), Chinese Academy of Sciences, during the last stages of this manuscript., In the context of scalar-tensor theories we study the evolution of the density contrast for Jordan-Fierz-Brans-Dicke theories in a Friedmann-Lemaitre-Robertson-Walker universe. Calculations are performed in the Einstein frame with the cosmological background described as Lambda-cold dark matter (Lambda CDM) and supplemented by a Jordan-Fierz-Brans-Dicke field. By using a completely general procedure valid for all scalar-tensor theories, we obtain the exact fourth-order differential equation for the density contrast evolution in modes of arbitrary size. In the case of sub-Hubble modes, the expression reduces to a simpler but still fourth-order equation that is then compared with the standard (quasistatic) approximation. Differences with respect to the evolution as predicted by the standard concordance Lambda CDM model are observed depending on the value of the coupling., Ministerio de Economía y Competitividad (MINECO), Actividad Investigadora CONSOLIDER - INGENIO - MULTIDARK (MINECO), Acciones Marie Skłodowska-Curie (UE), Generalitat de Catalunya, ACGC, University of Cape Town, Programa Beatriu de Pinós (BP-DGR), Unión Europea (UE), Depto. de Física Teórica, Fac. de Ciencias Físicas, TRUE, pub

© 2012 American Physical Society. We would like to thank Daniel Nieto for useful comments. This work has been supported by Ministerio de Ciencia y Innovación (Spain) project numbers FIS 2008- 01323, FPA 2008-00592, and Consolider-Ingenio Multimessenger Approach for Dark Matter Detection (MULTIDARK) CSD2009-00064. A. d. l. C.-D. also acknowledges the University Research Council, the National Research Foundation (South Africa), and Universidad Complutense de Madrid., Branons are new degrees of freedom that appear in flexible brane-world models corresponding to brane fluctuations. These new fields can behave as standard weakly interacting massive particles (WIMPs) with a significant associated thermal relic density. We analyze the present constraints from their spontaneous annihilations into photons for Energetic Gamma-Ray Experiment Telescope (EGRET), Fermi Large Area Telescope (LAT), and Major Atmospheric Gamma-Ray Imaging Cherenkov (MAGIC) telescopes, and the prospects for detection in future Cherenkov telescopes. In particular, we focus on possible signals coming from the Galactic center and different dwarf spheroidals, such as Draco, Sagittarius, Canis Major and SEGUE 1. We conclude that for those targets, present observations are below the sensitivity limits for branon detection by assuming standard dark matter distributions and no additional boost factors. However, future experiments such as the Cherenkov Telescope Array (CTA) could be able to detect gamma-ray photons coming from the annihilation of branons with masses higher than 150 GeV., Ministerio de Ciencia e Innovacion, Spain, Consolider-Ingenio Multimessenger Approach for Dark Matter Detection (MULTIDARK), Depto. de Física Teórica, Fac. de Ciencias Físicas, TRUE, pub

© 2012 American Physical Society. This work has been supported by MICINN (Spain) under Project Nos. FIS 2008-01323, FIS2011-23000, FPA2011- 27853 01 and Consolider-Ingenio MULTIDARK under Contract No. CSD2009-00064., We consider homogeneous Abelian vector fields in an expanding universe. We find a mechanical analogy in which the system behaves as a particle moving in three dimensions under the action of a central potential. In the case of bounded and rapid evolution compared to the rate of expansion, we show-by making use of the virial theorem-that for an arbitrary potential and polarization pattern, the average energy-momentum tensor is always diagonal and isotropic despite the intrinsic anisotropic evolution of the vector field. For simple power law potentials of the form V = lambda(A(mu)A(mu))(n), the average equation of state is found to be w = (n - 1)/(n + 1). This implies that vector coherent oscillations could act as natural dark matter or dark energy candidates. Finally, we show that under very general conditions, the average energy-momentum tensor of a rapidly evolving bounded vector field in any background geometry is always isotropic and has the perfect fluid form for any locally inertial observer., MICINN (Spain), Depto. de Física Teórica, Fac. de Ciencias Físicas, TRUE, pub

© 2012 American Physical Society. This work has been supported by MICINN (Spain) Projects No. FIS 2008-01323, No. FIS2011-23000, No. FPA2011-27853-01 and Consolider-Ingenio MULTIDARK CSD2009-00064. J.A.R. C. acknowledges the kind hospitality of the Institute of Theoretical Astrophysics at the University of Oslo, Norway, We show that the gamma ray spectrum observed with the HESS array of Cherenkov telescopes coming from the Galactic Center region and identified with the source HESS J1745-290 is well fitted by the secondary photons coming from dark matter (DM) annihilation over a diffuse power law background. The amount of photons and morphology of the signal localized within a region of few parsecs, require compressed DM profiles as those resulting from baryonic contraction, which offer 103 enhancements in the signal over DM alone simulations. The fitted background from HESS data is consistent with recent Fermi-LAT observations of the same region., MICINN (Spain), Depto. de Física Teórica, Fac. de Ciencias Físicas, TRUE, pub

© 2006 The American Physical Society. This work is partially supported by DGICYT (Spain) under project numbers FPA 2004-02602 and BFM 2002- 01003, by NSF grant No. PHY-0239817 and by the Fulbright-MEC (Spain) program., We study the possibility to explain the nonbaryonic dark matter abundance and improve the present fits on the muon anomalous magnetic moment through the same new physics. In this work we show that massive brane fluctuations (branons) in large extra-dimensions models can provide an economical way to deal with these two issues. This is so because the low-energy branon physics depends effectively on essentially only three parameters. Next collider experiments, such as LHC or ILC, will be sensitive to branon phenomenology in the natural parameter region where the theory is able to account for the two effects., DGICYT (Spain), NSF grant, Fulbright-MEC (Spain), Depto. de Física Teórica, Fac. de Ciencias Físicas, TRUE, pub

© 2004 The American Physical Society. We would like to thank J. Terrón, M. Vázquez, and M. Spiropulu for useful comments and experimental information. This work has been partially supported by the DGICYT (Spain) under Projects No. FPA2000-0956 and No. BFM2002-01003., In the context of the brane-world scenarios with compactified extra dimensions, we study the production of brane fluctuations (branons) in hadron colliders (p (p) over bar, pp, and e(+/-)p) in terms of the brane tension parameter f, the branon mass M, and the number of branons N. From the absence of monojet events at HERA and Tevatron (run I), we set bounds on these parameters and we also study how such bounds could be improved at Tevatron (run II) and the future LHC. The single-photon channel is also analyzed for the two last colliders., DGICYT (Spain), Depto. de Física Teórica, Fac. de Ciencias Físicas, TRUE, pub

©2003 The American Physical Society, We consider a general brane-world model parametrized by the brane tension scale f and the branon mass M. For a low tension compared to the fundamental gravitational scale, we calculate the relic branon abundance and its contribution to the cosmological dark matter. We compare this result with the current observational limits on the total and hot dark matter energy densities and derive the corresponding bounds on f and M. Using the nucleosynthesis bounds on the number of relativistic species, we also set a limit on the number of light branons in terms of the brane tension. Finally, we estimate the bounds coming from the energy loss rate in supernovae explosions due to massive branon emission., Depto. de Física Teórica, Fac. de Ciencias Físicas, TRUE, pub

© 2003 The American Physical Society. This work has been partially supported by the DGICYT (Spain) under Projects No. FPA 2000-0956 and No. BFM2000-1326., We show that, in the context of brane-world scenarios with low tension [tau]=f^4, massive brane fluctuations (branons) are natural dark matter candidates. We calculate the present abundances for both hot (warm) and cold branons in terms of the branon mass M and the tension scale f. The results are compared with the current experimental bounds on these parameters. We also study the prospects for their detection in direct search experiments and comment on their characteristic signals in the indirect ones., DGICYT (Spain), Depto. de Física Teórica, Fac. de Ciencias Físicas, TRUE, pub

©2001 The American Physical Society. This work was partially supported by the Ministerio de Educación y Ciencia (Spain) (CICYT AEN 97-1693 and PB98-0782), In the context of a brane world and including an induced curvature term in the brane action, we obtain the effective Lagrangian for the Goldstone bosons (branons) associated with the spontaneous breaking of the translational invariance in the bulk. In addition to the branons, this effective action has Skyrmion-like solitonic states which can be understood as holes in the brane. We study their main properties such as mass and size, the Skyrmion-branon interaction, and their possible fermionic quantization. We also consider states where the brane is wrapped around the extra dimensions and their relation with the brane-Skyrmions. Finally, we extend our results to higher-dimensional branes, such as those appearing in M theory, where brane-Skyrmions could also be present., Ministerio de Educación y Ciencia (Spain), Depto. de Física Teórica, Fac. de Ciencias Físicas, TRUE, pub