Mon - 06/14/21

There is no new related paper today

There is no new related paper today

Fri - 06/11/21

Primordial perturbations in kinetically dominated regimes of general relativity and hybrid quantum cosmology

  • Authors: Beatriz Elizaga Navascués, Rafael Jiménez-Llamas, Guillermo A. Mena Marugán
  • Subjects: General Relativity and Quantum Cosmology (gr-qc)
  • Arxiv link: https://arxiv.org/abs/2106.05628
  • Abstract Scalar fields with an energy density dominated by its kinetic part may have played a relevant role in the very early stages of the Universe. Compared to the standard inflationary paradigm, they may lead to modifications in observable quantities, e.g. the anisotropies found in the cosmic microwave background. Kinetically dominated regimes arise in classical fast-roll scenarios as well as in quantum bouncing cosmologies. For instance, kinetic dominance is typical in interesting preinflationary phases of Loop Quantum Cosmology. In this work, we analyze the leading-order effects that the presence of a scalar field potential causes on the primordial cosmological perturbations in these kinetically dominated epochs. These effects can be grouped in two sets, namely, those that affect the effective mass of the perturbations and those that affect the choice of their vacuum state. The effective mass is modified directly by terms that include the potential, but also indirectly by the change in the background dynamics and the relation between the parameterization of these dynamics and the conformal time, usually employed to describe the evolution of the perturbations. On the other hand, away from de Sitter inflation, the Bunch-Davies state is no longer the most natural vacuum at all scales. Recent proposals suggest to modify it by carrying out certain Hamiltonian diagonalization with a suitable asymptotic behavior at large wavenumber scales. Both this diagonalization condition and the imposed asymptotic behavior depend on the effective mass of the perturbations, and therefore the selected vacuum state varies in the presence of the scalar field potential.

There is no new related paper today

  1. [2106.05926] - Scalar Curvature Invariants in Classical and Quantum Gravity - B. Shakerin, D.D. McNutt, B. Mattingly, A. Kar, W. Julius, M. Gorban, C. Watson, P. Brown, J.S. Lee, E. W. Davis, G.B. Cleaver

  2. [2106.05912] - Causality and gravity - John F. Donoghue, Gabriel Menezes

  3. [2106.05803] - Pure Lorentz spin connection theories and uniqueness of General Relativity - Kirill Krasnov, Ermis Mitsou

Thu - 06/10/21

There is no new related paper today

Spin current in BF theory

  • Authors: Malik Matwi
  • Subjects: General Relativity and Quantum Cosmology (gr-qc)
  • Arxiv link: https://arxiv.org/abs/2106.04870
  • Abstract In this paper, we introduce a current which we call spin current corresponding to the variation of the matter action in BF theory with respect to the spin connection $A$ which takes values in Lie algebra $\mathfrak{so}(3,\mathbb{C})$ in self-dual formalism. For keeping the constraint $DB^i=0$ satisfied, we suggest adding a new term to the BF Lagrangian using a new field $\psi^i$ which can be used for calculating the spin current. We derive the equations of motion and discuss the solutions. We will see that the solutions of that equations do not require a specific metric on the manifold $M$, we just need to know the symmetry of the system and the information about the spin current. Finally we find the solutions in a spherical and cylindrical symmetric systems.

  1. [2106.04604] - Dressing in AdS and a Conformal Bethe-Salpeter Equation - Sylvain Fichet

  2. [2106.04606] - Notes on flat-space limit of AdS/CFT - Yue-Zhou Li

Wed - 06/09/21

Keyword: loop quantum gravity

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Keyword: spin foam

There is no new related paper today

  1. [2106.04141] - Maximal momentum GUP leads to Stelle gravity - Vijay Nenmeli, S. Shankaranarayanan (IIT Bombay), Vasil Todorinov, Saurya Das (University of Lethbridge)

  2. [2106.04226] - Constraints on Global Symmetry Breaking in Quantum Gravity from Cosmic Birefringence Measurements - James Alvey, Miguel Escudero Abenza

  3. [2106.04532] - The two-sphere partition function in two-dimensional quantum gravity at fixed area - Beatrix Mühlmann

Tue - 06/08/21

Keyword: loop quantum gravity

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Keyword: spin foam

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Mon - 06/07/21

Keyword: loop quantum gravity

Cosmic tangle: Loop quantum cosmology and CMB anomalies

  • Authors: Martin Bojowald
  • Subjects: General Relativity and Quantum Cosmology (gr-qc); Cosmology and Nongalactic Astrophysics (astro-ph.CO); High Energy Physics - Theory (hep-th)
  • Arxiv link: https://arxiv.org/abs/2106.02481
  • Abstract: Loop quantum cosmology is a conflicted field in which exuberant claims of observability coexist with serious objections against the conceptual and physical viability of its current formulations. This contribution presents a non-technical case study of the recent claim that loop quantum cosmology might alleviate anomalies in observations of the cosmic microwave background.

Keyword: spin foam

There is no new paper today