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Momentum transfer in the dark sector ABSTRACT DESI 2024 VI: Cosmological Constraints from the Measurements of Baryon Acoustic Oscillations Resumen Datos de la conferenciante Rotating galactic black holes A class of cosmological models with spatially constant sign-changing curvature TITLE: Counting microstates of black holes with the semiclassical path integral SPEAKER: Martin Sasieta (Brandeis University, US) ABSTRACT: In this talk I will construct an infinite family of microstates with geometric interiors for eternal black holes in TITLE: The correspondence principle between rotating black holes and fundamental strings SPEAKER: Marija Tomašević (University of Amsterdam) ABSTRACT: The correspondence principle between strings and black holes is a TITLE: A simple model for the cosmological sector of loop quantum gravity SPEAKER: Álvaro Cendal, (Universidad Complutense de Madrid & IPARCOS) ABSTRACT: We study the truncation of loop quantum gravity (LQG) known as the Host: Miguel ABSTRACT TITLE: Particle versus Wave Dark Matter in Deep Space Data from JWST SPEAKER: Tom Broadhurst (UPV/EHU) ABSTRACT: We have discovered in that lensed galaxies intersected by Creation of an inflationary universe out of a black hole TITLE: Role of Stellar Microlensing in Generating Cluster Gravitationally-Lensed Transients The polyhomogeneity of the gravitational field and conserved ABSTRACT: Geodesic Completeness in General Cosmological Scenarios, by William Kinney, Univ. of Buffalo, US. ABSTRACT: Do Black Holes have Singularities? https://arxiv.org/abs/2312.00841 Microsoft Teams ¿Necesita ayuda? TITLE: Solitons in Quantum Field Theory
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ABSTRACT:
In this talk, I will explain the elastic interactions in the dark sector which are described phenomenologically by a momentum
transfer coupling, modifying only the linear and non-linear cosmological perturbations but not the background cosmology. I will
show how non-altering background interactions can have measurable imprints in observables like the matter power spectrum
or how they can alleviate the σ_8 tension, and the possible effects on the bias or on the relative velocity of matter components.
Finally, I will explain how those couplings can alter the non-linear process of formation of structures.
The basis for the standard model in Cosmology is the Robertson-Walker
(RW) spacetime. The geometric nature of gravity makes the geometric characterization of
spacetimes of great importance. The characterizations of the RW geometry involve several
kinds of ingredients with different geometrical/physical/observational weight, and different
characterizations probe different aspects of the theory. The aim of this work is two-fold. We
establish a novel geometric characterization of the RW spacetime, involving an arbitrary
single observer and, along the process, we find a canonical form of the RW metric associated
to any such single observer equipped with an arbitrary space frame.
https://arxiv.org/abs/2404.03002
La cosmología moderna nos propone una reconstrucción intrigante de la historia del Universo, desde el Big Bang hasta hoy. Entre sus “enigmas conocidos” se encuentran la materia oscura, la energía oscura y el origen de las fluctuaciones primordiales de densidad que dieron origen a las galaxias. Repasaremos brevemente la evidencia científica que está detrás del “modelo estándar de la cosmología” y algunos de sus retos pendientes. Entre ellos, la idea de que ciertos procesos cuánticos en el momento del Big Bang dejaron trazas en la distribución de materia en el universo que todavía hoy se pueden detectar.
Quizá sea posible “ver” el comienzo del universo con telescopios!
Ana Achúcarro es Catedrática de Física Teórica en la Universidad de Leiden (Países Bajos) desde 2002 y en la UPV-EHU desde 1999, actualmente en excelencia y afiliada al EHU Quantum Center. Su investigación se centra en el Universo primitivo, (super)gravedad, solitones, branas y agujeros negros. Licenciada en Física en UPV-EHU, se doctoró en la Universidad de Cambridge (1989) en el Grupo de Relatividad que dirigía Stephen Hawking. Su trabajo de Tesis Doctoral con Paul Townsend introdujo el término brana en la literatura científica. Tras estancias postdoctorales en Imperial College (Londres) y Tufts University (Boston), obtuvo la titularidad en la UPV-EHU en 1994. Fue la primera mujer Catedrática de Física Teórica en los Países Bajos, donde también recibió la prestigiosa beca personal VICI (2004-2010), fue coautora del primer Plan Nacional Estratégico de Física de Astropartículas, e Investigadora Principal del Programa FOM de Cosmología “Observar el Big Bang” (2014-2022). Fue miembro del Comité Científico Asesor del CSIC (2011-2017). Entre 2011-2017 organizó para la Fundación BBVA la serie de conferencias de divulgación “La Ciencia del Cosmos, la Ciencia en el Cosmos”. Fue elegida miembro de la Academia Europea en 2011.
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https://arxiv.org/abs/2403.19933
https://arxiv.org/abs/2209.11184
general relativity with a negative cosmological constant. Wormholes in the Euclidean path integral for gravity cause these states
to have small, but nonzero, quantum mechanical overlaps that have a universal form. The overlaps have a dramatic consequence:
the microstates span a Hilbert space of log dimension equal to the Bekenstein-Hawking entropy. The construction does not depend
on details of the black hole, and can include general quantum corrections, near or far from extremality. For supersymmetric black
holes, these microstates differ from other recent constructions in that the interior excitations are not confined within the near-extremal
throat. I will end by mentioning open problems and future directions.
general framework for matching black holes and massive states of fundamental strings
at a point where their physical properties (such as mass, entropy and temperature) smoothly
agree with each other. This correspondence becomes puzzling when attempting to include
rotation: At large enough spins, there exist degenerate string states that seemingly cannot
be matched to any black hole. Conversely, there exist black holes with arbitrarily large spins
that cannot correspond to any single-string state. We discuss in detail the properties of both
types of objects and find that a correspondence that resolves the puzzles is possible
by adding dynamical features and non-stationary configurations to the picture. Our scheme
incorporates all black hole and string phases as part of the correspondence, save for one
outlier which remains enigmatic: the near-extremal Kerr black hole. Along the way, we elaborate
on general aspects of the correspondence that have not been emphasized before.
2-vertex model. This simple model allows us to gain insight on the implementation of the
dynamics and on the search of a cosmological sector within the theory (among the main
open problems of LQG). We will present the classical dynamics of the model and we will
show the relation of a reduced sector with the dynamics of loop quantum cosmology (LQC).
June 2024
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Einstein rings are continuously twinkling in deep JWST images. This is caused when
micro-lensing caustics of stars in the lensing galaxy sweep over the surface of
individual stars within the lensed galaxy, allows us to detect individual stars at
cosmological distances apparently switching on and off.
These detections we find favour the inner edge of the Einstein ring with a
broad asymmetric spread that we show is characteristic of Wave Dark Matter as
a Bose Einstein Condensate, of very light axions, 10^{-22}eV, with a de Broglie
wavelength on astronomical scales and motivated by String Theory. Conventional
heavy particle Dark Matter (CDM) predicts the opposite behaviour and appears
excluded. This conclusion is now reinforced by the tendency for the most distant
galaxies to be elongated in shape in JWST images of well resolved high redshift
galaxies. Our cosmological simulations show this effect can be explained
by Wave and Warm Dark Matter, where galaxies form steadily at the nodes of long smooth
filaments as dark matter, stars and gas rain down for an extended period of about 0.5Gyrs.
This is quite unlike CDM where galaxies form from fragmented filaments and frequently merge, so that young galaxy shapes are expected to be oblate spheroids, in tension the observed young galaxies at high redshift observed by JWST. We outline further definitive predictions for comparison with ongoing JWST surveys.
https://arxiv.org/abs/1601.03929
SPEAKER: Sung Kei Li (University of Hong Kong)
ABSTRACT:
This seminar focuses on the impact of stellar microlensing on transients composed of lensed young star clusters, specifically H-II regions,
within the renowned ”Dragon Arc.” The Dragon Arc is an actively star-forming galaxy at a redshift of ∼ 0.73, multiply-lensed by the foreground
galaxy cluster Abell 370. During the Flashlights” project, two deep observations of Abell 370 taken roughly a year apart revealed brightness
variations spatially coinciding with the young star clusters in the Dragon Arc. Unlike conventional transients, where a single stellar source
remains consistently undetectable, these young star cluster transients, comprising numerous stars, persist over time, and the precise effects
of stellar microlensing remains understudied.
By employing a newly developed simulation, we examine the role of stellar microlensing in generating lensed star cluster transients. The simulation
predicts a detection rate of lensed star cluster transients that aligns with the observed data within a 1σ uncertainty range, suggesting that stellar
microlensing alone can account for all the detected lensed star cluster transients. Furthermore, this consistency enables the imposition of constraints
on the abundance of primordial black holes in dark matter, reaching a confidence level of 3σ, with constraints as stringent as ≤ 1%.
charges at null infinity, by Edgar Gasperín, CENTRA (Lisbon)
In this talk we will give an overview of the conformal Einstein field equations (CEFEs) and briefly discuss some of
the global non-linear stability results obtained with the CEFEs in asymptotically flat and de-Sitter-like spacetimes.
Motivated the caveats that emerge from these results, we will discuss the problem at spatial infinity and its impact
(polyhomogeneity) on the peeling behaviour of the gravitational field. To give a simple but illustrative discussion of
the so-called cylinder at spatial infinity (i^0), we will focus the analysis on the polyhomogeneity of spin-0 fields in
Minkowski spacetime propagating close to the cylinder at i^0 and the calculation of conserved charges at the critical
sets where spatial and null infinity meet.
The well-known Borde-Guth-Vilenkin Theorem shows that inflationary spacetimes are generically
geodesically past-incomplete, necessitating the existence of a pre-inflationary boundary of some sort, possibly singular.
In this talk, I discuss the generalization of the BGV theorem to spactimes beyond inflation, including inhomogeneous
and cyclic models. I argue that the cyclic model proposed by Ijjas and Steinhardt is geodesically incomplete, and that
an asymptotically de Sitter version of Penrose’s Conformal Cyclic Cosmology is either past- or future-incomplete.
July 2024
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Unirse a la reunión ahora
Id. de reunión: 337 116 539 27
Código de acceso: kgQJzY
________________________________
Unirse en un dispositivo de videoconferencia
Clave de inquilino: teams@tecnalia.com
Id. del vídeo: 127 553 223 3
Más información
Para organizadores: Opciones de la reunión
SPEAKER: Jarah Evslin, Institute of Modern Physics, China
ABSTRACT:
Solitons in quantum field theory correspond to states. We present a new formalism for treating
these states. The formalism is much simpler and easier to use than previous formalisms, making many
previously impractical problems now practical. We have used it to calculate soliton masses, spectra, form factors,
and scattering amplitudes, as well as the decay rates of excited solitons. Our long-term goal is to treat the
monopoles whose condensation may be responsible for confinement in QCD.
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