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9 results on '"Early Universe physics"'

1. Symmetries, unitarity and positivity of cosmological effective field theories

Author

Grall, Tanguy and Pajer, Enrico

Subjects
cosmology, early universe physics, quantum field theory
Abstract

Cosmology poses unique theoretical challenges at the interface between Quantum Field Theory (QFT) and General Relativity (GR). The time dependence of cosmological spacetimes, upon which quantum fields propagate, spontaneously breaks time translation and Lorentz boost invariance. Thus the usual tools of particle physics, which assume full Lorentz invariance, need to be adapted to the study of cosmological theories. Using Effective Field Theory (EFT) techniques, universal predictions can be made about the dynamics of fluctuations around cosmological backgrounds (e.g. the EFT of Inflation). However, exploring the structure of these cosmological EFTs, such as their regime of validity, still requires tools adapted to their particular set of symmetries. In this thesis we focus on the sub-horizon regime of cosmological EFTs, where the effect of the background curvature can be neglected. This leads us to study flat space EFTs around time-dependent vacua. We explore the landscape of such theories whose structure is fixed by additional symmetries. We show how to modify EFT power counting rules and perturbative unitarity methods when Lorentz boosts are spontaneously broken. This allows us to determine the region of parameter space for which cosmological EFTs are weaklycoupled on sub-horizon scales. Finally we provide a new way to derive positivity bounds and constrain which parts of this parameter space admit unitary and causal UV completions. Comparing with observational constraints on primordial non-Gaussianities, they give us new ways to unravel the physics of inflation.

Published
2022
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2. Gravitation and the Universe from large scale-structures: The GAUSS mission concept Mapping the cosmic web up to the reionization era.

Author

Blanchard, Alain, Aubourg, Éric, Brax, Philippe, Castander, Francisco J., Codis, Sandrine, Escoffier, Stéphanie, Dournac, Fabien, Ferté, Agnès, Finelli, Fabio, Fosalba, Pablo, Gangler, Emmanuel, Gontcho, Satya Gontcho A, Hawken, Adam, Ilić, Stéphane, Kneib, Jean-Paul, Kunz, Martin, Lavaux, Guilhem, Le Fèvre, Olivier, Lesgourgues, Julien, and Mellier, Yannick

Subjects
*INFLATIONARY universe, *CONCEPT mapping, *DARK energy, *PROPERTIES of matter, *GRAVITATION, UNIVERSE
Abstract

Today, thanks in particular to the results of the ESA Planck mission, the concordance cosmological model appears to be the most robust to describe the evolution and content of the Universe from its early to late times. It summarizes the evolution of matter, made mainly of dark matter, from the primordial fluctuations generated by inflation around 10− 30 second after the Big Bang to galaxies and clusters of galaxies, 13.8 billion years later, and the evolution of the expansion of space, with a relative slowdown in the matter-dominated era and, since a few billion years, an acceleration powered by dark energy. But we are far from knowing the pillars of this model which are inflation, dark matter and dark energy. Comprehending these fundamental questions requires a detailed mapping of our observable Universe over the whole of cosmic time. The relic radiation provides the starting point and galaxies draw the cosmic web. JAXA's LiteBIRD mission will map the beginning of our Universe with a crucial test for inflation (its primordial gravity waves), and the ESA Euclid mission will map the most recent half part, crucial for dark energy. The mission concept GAUSS, described in this White Paper, aims at being a mission to fully map the cosmic web up to the reionization era, linking early and late evolution, to tackle and disentangle the crucial degeneracies persisting after the Euclid era between dark matter and inflation properties, dark energy, structure growth and gravitation at large scale. [ABSTRACT FROM AUTHOR]

Published
2021
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3. 国际哲学与科学交叉学科研究 进展评述.

Author

刘 闯 and 朱科夫

Abstract

In this article we discuss a selected sample of interdisciplinary researches between philosophy and science in the forefront of high energy physics, science of intelligence, biological science, and social science. We discuss both the ideas and the important international institutions and figures. [ABSTRACT FROM AUTHOR]

Published
2021
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4. Symmetries, unitarity and positivity of cosmological effective field theories

Author

Grall, Tanguy

Subjects
early universe physics, cosmology, quantum field theory
Abstract

Cosmology poses unique theoretical challenges at the interface between Quantum Field Theory (QFT) and General Relativity (GR). The time dependence of cosmological spacetimes, upon which quantum fields propagate, spontaneously breaks time translation and Lorentz boost invariance. Thus the usual tools of particle physics, which assume full Lorentz invariance, need to be adapted to the study of cosmological theories. Using Effective Field Theory (EFT) techniques, universal predictions can be made about the dynamics of fluctuations around cosmological backgrounds (e.g. the EFT of Inflation). However, exploring the structure of these cosmological EFTs, such as their regime of validity, still requires tools adapted to their particular set of symmetries. In this thesis we focus on the sub-horizon regime of cosmological EFTs, where the effect of the background curvature can be neglected. This leads us to study flat space EFTs around time-dependent vacua. We explore the landscape of such theories whose structure is fixed by additional symmetries. We show how to modify EFT power counting rules and perturbative unitarity methods when Lorentz boosts are spontaneously broken. This allows us to determine the region of parameter space for which cosmological EFTs are weaklycoupled on sub-horizon scales. Finally we provide a new way to derive positivity bounds and constrain which parts of this parameter space admit unitary and causal UV completions. Comparing with observational constraints on primordial non-Gaussianities, they give us new ways to unravel the physics of inflation., Cambridge Trust

Published
2023
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5. The Effect of a Positive Cosmological Constant on the Bounce of Loop Quantum Cosmology

Author

Mercedes Martín-Benito and Rita B. Neves

Subjects
loop quantum cosmology, quantum bounce, cosmological constant, early universe physics, Mathematics, QA1-939
Abstract

We provide an analytical solution to the quantum dynamics of a flat Friedmann-Lemaître- Robertson-Walker model with a massless scalar field in the presence of a small and positive cosmological constant, in the context of Loop Quantum Cosmology. We use a perturbative treatment with respect to the model without a cosmological constant, which is exactly solvable. Our solution is approximate, but it is precisely valid at the high curvature regime where quantum gravity corrections are important. We compute explicitly the evolution of the expectation value of the volume. For semiclassical states characterized by a Gaussian spectral profile, the introduction of a positive cosmological constant displaces the bounce of the solvable model to lower volumes and to higher values of the scalar field. These displacements are state dependent, and in particular, they depend on the peak of the Gaussian profile, which measures the momentum of the scalar field. Moreover, for those semiclassical states, the bounce remains symmetric, as in the vanishing cosmological constant case. However, we show that the behavior of the volume is more intricate for generic states, leading in general to a non-symmetric bounce.

Published
2020
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6. Gravitation and the Universe from large scale-structures: The GAUSS mission concept Mapping the cosmic web up to the reionization era

Author

Stéphane Ilić, Emmanuel Gangler, Safir Yahia-Cherif, A. J. Hawken, Yann Rasera, Satya Gontcho A Gontcho, Jean-Paul Kneib, E. Aubourg, Norma G. Sanchez, Alain Blanchard, Guilhem Lavaux, Sandrine Codis, Julien Lesgourgues, Yannick Mellier, Olivier Le Fevre, C. Renault, Agnès Ferté, Fabien Dournac, Z. Sakr, Stephanie Escoffier, I. Tutusaus, M. Ricci, Philippe Brax, Pablo Fosalba, Fabio Finelli, Jérémy Neveu, Francisco J. Castander, Martin Kunz, Institut de recherche en astrophysique et planétologie (IRAP), Université Toulouse III - Paul Sabatier (UT3), Université de Toulouse (UT)-Université de Toulouse (UT)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire Midi-Pyrénées (OMP), Institut de Recherche pour le Développement (IRD)-Université Toulouse III - Paul Sabatier (UT3), Université de Toulouse (UT)-Université de Toulouse (UT)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National d'Études Spatiales [Toulouse] (CNES)-Centre National de la Recherche Scientifique (CNRS)-Météo-France -Institut de Recherche pour le Développement (IRD)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National d'Études Spatiales [Toulouse] (CNES)-Centre National de la Recherche Scientifique (CNRS)-Météo-France -Centre National de la Recherche Scientifique (CNRS), AstroParticule et Cosmologie (APC (UMR_7164)), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Institut National de Physique Nucléaire et de Physique des Particules du CNRS (IN2P3)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Centre National de la Recherche Scientifique (CNRS)-Université Paris Cité (UPCité), Institut de Physique Théorique - UMR CNRS 3681 (IPHT), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS), Institut d'Astrophysique de Paris (IAP), Institut national des sciences de l'Univers (INSU - CNRS)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS), Centre de Physique des Particules de Marseille (CPPM), Aix Marseille Université (AMU)-Institut National de Physique Nucléaire et de Physique des Particules du CNRS (IN2P3)-Centre National de la Recherche Scientifique (CNRS), Laboratoire de Physique de Clermont (LPC), Institut National de Physique Nucléaire et de Physique des Particules du CNRS (IN2P3)-Centre National de la Recherche Scientifique (CNRS)-Université Clermont Auvergne (UCA), Laboratoire d'Etude du Rayonnement et de la Matière en Astrophysique et Atmosphères = Laboratory for Studies of Radiation and Matter in Astrophysics and Atmospheres (LERMA), École normale supérieure - Paris (ENS-PSL), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS)-CY Cergy Paris Université (CY), Laboratoire d'Astrophysique de Marseille (LAM), Aix Marseille Université (AMU)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National d'Études Spatiales [Toulouse] (CNES)-Centre National de la Recherche Scientifique (CNRS), Laboratoire de l'Accélérateur Linéaire (LAL), Université Paris-Sud - Paris 11 (UP11)-Institut National de Physique Nucléaire et de Physique des Particules du CNRS (IN2P3)-Centre National de la Recherche Scientifique (CNRS), Laboratoire Univers et Théories (LUTH (UMR_8102)), Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université Paris Diderot - Paris 7 (UPD7)-Centre National de la Recherche Scientifique (CNRS), Laboratoire de Physique Subatomique et de Cosmologie (LPSC), Institut National de Physique Nucléaire et de Physique des Particules du CNRS (IN2P3)-Centre National de la Recherche Scientifique (CNRS)-Université Grenoble Alpes (UGA)-Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP ), Université Grenoble Alpes (UGA), Laboratoire d'Annecy de Physique des Particules (LAPP), Institut National de Physique Nucléaire et de Physique des Particules du CNRS (IN2P3)-Université Savoie Mont Blanc (USMB [Université de Savoie] [Université de Chambéry])-Centre National de la Recherche Scientifique (CNRS), Institut national des sciences de l'Univers (INSU - CNRS)-Université Toulouse III - Paul Sabatier (UT3), Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées-Observatoire Midi-Pyrénées (OMP), Météo France-Centre National d'Études Spatiales [Toulouse] (CNES)-Université Fédérale Toulouse Midi-Pyrénées-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche pour le Développement (IRD)-Météo France-Centre National d'Études Spatiales [Toulouse] (CNES)-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche pour le Développement (IRD)-Centre National de la Recherche Scientifique (CNRS), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Centre National de la Recherche Scientifique (CNRS)-Université de Paris (UP), Laboratoire d'Etude du Rayonnement et de la Matière en Astrophysique (LERMA (UMR_8112)), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS)-CY Cergy Paris Université (CY), Centre National de la Recherche Scientifique (CNRS)-Institut National de Physique Nucléaire et de Physique des Particules du CNRS (IN2P3)-Université Paris-Sud - Paris 11 (UP11), and Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Centre National de la Recherche Scientifique (CNRS)-Université Paris Diderot - Paris 7 (UPD7)

Subjects
Big Bang, dark energy: parametrization, satellite: Planck, Primordial fluctuations, media_common.quotation_subject, Dark matter, Observable universe, Astrophysics::Cosmology and Extragalactic Astrophysics, 7. Clean energy, 01 natural sciences, Cosmology, dark matter: parametrization, symbols.namesake, cosmological model: parameter space, 0103 physical sciences, ionization, Dark energy, structure, [PHYS.PHYS.PHYS-INS-DET]Physics [physics]/Physics [physics]/Instrumentation and Detectors [physics.ins-det], Planck, 010303 astronomy & astrophysics, media_common, Physics, 010308 nuclear & particles physics, fluctuation: primordial, Astrophysics::Instrumentation and Methods for Astrophysics, big bang, Astronomy, Astronomy and Astrophysics, space, acceleration, tensor, Universe, inflation: model, 13. Climate action, Space and Planetary Science, gravitation, symbols, galaxy: cluster, [PHYS.ASTR]Physics [physics]/Astrophysics [astro-ph], Early Universe physics
Abstract

Blanchard, A., et al., Today, thanks in particular to the results of the ESA Planck mission, the concordance cosmological model appears to be the most robust to describe the evolution and content of the Universe from its early to late times. It summarizes the evolution of matter, made mainly of dark matter, from the primordial fluctuations generated by inflation around 10 second after the Big Bang to galaxies and clusters of galaxies, 13.8 billion years later, and the evolution of the expansion of space, with a relative slowdown in the matter-dominated era and, since a few billion years, an acceleration powered by dark energy. But we are far from knowing the pillars of this model which are inflation, dark matter and dark energy. Comprehending these fundamental questions requires a detailed mapping of our observable Universe over the whole of cosmic time. The relic radiation provides the starting point and galaxies draw the cosmic web. JAXA’s LiteBIRD mission will map the beginning of our Universe with a crucial test for inflation (its primordial gravity waves), and the ESA Euclid mission will map the most recent half part, crucial for dark energy. The mission concept GAUSS, described in this White Paper, aims at being a mission to fully map the cosmic web up to the reionization era, linking early and late evolution, to tackle and disentangle the crucial degeneracies persisting after the Euclid era between dark matter and inflation properties, dark energy, structure growth and gravitation at large scale.

Published
2021
Full Text
View/download PDF

7. The Effect of a Positive Cosmological Constant on the Bounce of Loop Quantum Cosmology

Author

Martín Benito, Mercedes, Neves, Rita B., Martín Benito, Mercedes, and Neves, Rita B.

Abstract

We provide an analytical solution to the quantum dynamics of a flat Friedmann-Lemaître- Robertson-Walker model with a massless scalar field in the presence of a small and positive cosmological constant, in the context of Loop Quantum Cosmology. We use a perturbative treatment with respect to the model without a cosmological constant, which is exactly solvable. Our solution is approximate, but it is precisely valid at the high curvature regime where quantum gravity corrections are important. We compute explicitly the evolution of the expectation value of the volume. For semiclassical states characterized by a Gaussian spectral profile, the introduction of a positive cosmological constant displaces the bounce of the solvable model to lower volumes and to higher values of the scalar field. These displacements are state dependent, and in particular, they depend on the peak of the Gaussian profile, which measures the momentum of the scalar field. Moreover, for those semiclassical states, the bounce remains symmetric, as in the vanishing cosmological constant case. However, we show that the behavior of the volume is more intricate for generic states, leading in general to a non-symmetric bounce., Ministerio de Ciencia e Innovación (MICINN)/FEDER, Fundação para a Ciência e a Tecnologia (FCT), Depto. de Física Teórica, Fac. de Ciencias Físicas, TRUE, pub

Published
2020

8. The missing link in gravitational-wave astronomy : discoveries waiting in the decihertz range

Author

Sedda, Manuel Arca, Berry, Christopher P. L., Jani, Karan, Amaro-Seoane, Pau, Auclair, Pierre, Baird, Jonathon, Baker, Tessa, Berti, Emanuele, Breivik, Katelyn, Burrows, Adam, Caprini, Chiara, Chen, Xian, Doneva, Daniela, Ezquiaga, Jose M., Ford, K. E. Saavik, Katz, Michael L., Kolkowitz, Shimon, McKernan, Barry, Mueller, Guido, Nardini, Germano, Pikovski, Igor, Rajendran, Surjeet, Sesana, Alberto, Shao, Lijing, Tamanini, Nicola, Vartanyan, David, Warburton, Niels, Witek, Helvi, Wong, Kaze, Zevin, Michael, Sedda, Manuel Arca, Berry, Christopher P. L., Jani, Karan, Amaro-Seoane, Pau, Auclair, Pierre, Baird, Jonathon, Baker, Tessa, Berti, Emanuele, Breivik, Katelyn, Burrows, Adam, Caprini, Chiara, Chen, Xian, Doneva, Daniela, Ezquiaga, Jose M., Ford, K. E. Saavik, Katz, Michael L., Kolkowitz, Shimon, McKernan, Barry, Mueller, Guido, Nardini, Germano, Pikovski, Igor, Rajendran, Surjeet, Sesana, Alberto, Shao, Lijing, Tamanini, Nicola, Vartanyan, David, Warburton, Niels, Witek, Helvi, Wong, Kaze, and Zevin, Michael

Abstract

The gravitational-wave astronomical revolution began in 2015 with LIGO's observation of the coalescence of two stellar-mass black holes. Over the coming decades, ground-based detectors like laser interferometer gravitational-wave observatory (LIGO), Virgo and KAGRA will extend their reach, discovering thousands of stellar-mass binaries. In the 2030s, the space-basedlaser interferometer space antenna(LISA) will enable gravitational-wave observations of the massive black holes in galactic centres. Between ground-based observatories and LISA lies the unexplored dHz gravitational-wave frequency band. Here, we show the potential of adecihertz observatory(DO) which could cover this band, and complement discoveries made by other gravitational-wave observatories. The dHz range is uniquely suited to observation of intermediate-mass (similar to 10(2)-10(4)M(circle dot)) black holes, which may form the missing link between stellar-mass and massive black holes, offering an opportunity to measure their properties. DOs will be able to detect stellar-mass binaries days to years before they merge and are observed by ground-based detectors, providing early warning of nearby binary neutron star mergers, and enabling measurements of the eccentricity of binary black holes, providing revealing insights into their formation. Observing dHz gravitational-waves also opens the possibility of testing fundamental physics in a new laboratory, permitting unique tests of general relativity (GR) and the standard model of particle physics. Overall, a DO would answer outstanding questions about how black holes form and evolve across cosmic time, open new avenues for multimessenger astronomy, and advance our understanding of gravitation, particle physics and cosmology.

Published
2020
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9. The Effect of a Positive Cosmological Constant on the Bounce of Loop Quantum Cosmology.

Author

Martín-Benito, Mercedes and Neves, Rita B.

Subjects
*QUANTUM cosmology, *COSMOLOGICAL constant, *PHYSICAL cosmology, *QUANTUM gravity, *QUANTUM theory, *CURVATURE, *SCALAR field theory, *ANALYTICAL solutions
Abstract

We provide an analytical solution to the quantum dynamics of a flat Friedmann-Lemaître- Robertson-Walker model with a massless scalar field in the presence of a small and positive cosmological constant, in the context of Loop Quantum Cosmology. We use a perturbative treatment with respect to the model without a cosmological constant, which is exactly solvable. Our solution is approximate, but it is precisely valid at the high curvature regime where quantum gravity corrections are important. We compute explicitly the evolution of the expectation value of the volume. For semiclassical states characterized by a Gaussian spectral profile, the introduction of a positive cosmological constant displaces the bounce of the solvable model to lower volumes and to higher values of the scalar field. These displacements are state dependent, and in particular, they depend on the peak of the Gaussian profile, which measures the momentum of the scalar field. Moreover, for those semiclassical states, the bounce remains symmetric, as in the vanishing cosmological constant case. However, we show that the behavior of the volume is more intricate for generic states, leading in general to a non-symmetric bounce. [ABSTRACT FROM AUTHOR]

Published
2020
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