Fri - 11/19/21

There is no new related paper today

There is no new related paper today

  1. [2111.09331] - Embedding Causal Sets into Minkowski Spacetime - Steven Johnston

Tue - 11/16/21

Gravitational lensing by a black hole in effective loop quantum gravity

  • Authors: Qi-Ming Fu, Xin Zhang
  • Subjects: General Relativity and Quantum Cosmology (gr-qc); High Energy Physics - Phenomenology (hep-ph); High Energy Physics - Theory (hep-th)
  • Arxiv link: https://arxiv.org/abs/2111.07223
  • Abstract It is well known that general relativity is an effective theory of gravity at low energy scale, and actually quantum effects cannot be ignored in the strong-field regime. As a strong gravitational object, black hole plays a key role in testing the quantum effects of gravity in the strong-field regime. In this paper, we focus on black hole in effective loop quantum gravity and investigate what the influences are of the quantum effects on the weak and strong bending angles of light rays. We find that this black hole could be a Schwarzschild black hole, a regular black hole, a one-way traversable wormhole, or a two-way traversable wormhole for the different values of the quantum parameter, and the strong bending angle for this compact object exhibits two different divergent behaviors, i.e., the logarithmic divergence and non-logarithmic divergence. There are a series of relativistic images on both sides of the optical axis. Only the outermost one can be resolved as a single image, and all others are packed together at the limiting angular position. It is interesting to note that the angular separation between the outermost relativistic image and the others initially increases and then decreases as the quantum parameter increases, indicating that there is a maximum in the angular separation. The maximum is reached after the black hole becomes a wormhole, which can be taken as a signal for the formation of the wormhole. Moreover, the limiting angular position decreases as the quantum parameter increases but a little bounce occurs after the formation of the wormhole, and the relative magnification in magnitudes first decreases and then increases as the quantum parameter increases.

Power spectrum for perturbations in an inflationary model for a closed universe

  • Authors: Claus Kiefer, Tatevik Vardanyan
  • Subjects: General Relativity and Quantum Cosmology (gr-qc); Cosmology and Nongalactic Astrophysics (astro-ph.CO)
  • Arxiv link: https://arxiv.org/abs/2111.07835
  • Abstract We derive the power spectrum of primordial quantum fluctuations in an inflationary universe for curvature parameter ${\mathcal K}=1$. This is achieved through a Born–Oppenheimer type of approximation scheme from the Wheeler–DeWitt equation of canonical quantum gravity using gauge-invariant variables. Compared to the flat model, the closed model exhibits a deficit of power at large scales.

There is no new related paper today

  1. [2111.07817] - Gravity from symmetry breaking phase transition - G.E. Volovik

  2. [2111.07828] - Considerations on Quantum Gravity Phenomenology - Carlo Rovelli

  3. [2111.07718] - Holographic Abrikosov lattice: vortex matter from black hole - Chuan-Yin Xia, Hua-Bi Zeng, Yu Tian, Chiang-Mei Chen, Jan Zaanen

  4. [2111.07816] - Allowable complex metrics in minisuperspace quantum cosmology - Jean-Luc Lehners

Mon - 11/15/21

There is no new related paper today

Towards the Finite-$N$ Twisted Holography from the Geometry of Phase Space

  • Authors: Seyed Faroogh Moosavian, Yehao Zhou
  • Subjects: High Energy Physics - Theory (hep-th); Algebraic Geometry (math.AG); Quantum Algebra (math.QA); Representation Theory (math.RT)
  • Arxiv link: https://arxiv.org/abs/2111.06876
  • Abstract We study a certain subalgebra of functions on the phase space of $2d$ BF theory with the gauge group $\mathrm{GL}_N$ coupled to a $1d$ quantum mechanics with global symmetry $\mathrm{GL}_K$ and its quantization. These functions are gauge-invariant local observables of the coupled theory, which appears as boundary side of an early example of twisted holography involving stacks of $N$ D2-branes and $K$ D4-branes intersecting along a real line. We give a geometric proof that the quantization of this subalgebra in the large-$N$ limit is the Yangian. The finite-$N$ subalgebra is a quotient of its large-$N$ limit by a certain ideal. We compute this ideal for $N=1$ and give an abstract characterization of the ideal for any $N$. Furthermore, we study the full algebra of functions on the phase space and prove that in the large-$N$ limit, it is the algebra of functions on the based loop group of $\mathrm{GL}_K\times \mathrm{GL}_1$. Similar to its subalgebra, the full finite-$N$ algebra is a quotient of the large-$N$ limit algebra by a certain ideal. We compute this ideal for $N=1$ and give an abstract characterization of the ideal for any $N$. Finally, we compute the Hilbert series of the full finite-$N$ algebra.

  1. [2111.06488] - Quasinormal modes of the Hayward black hole surrounded by quintessence: scalar, electromagnetic and gravitational perturbations - Omar Pedraza, L. A. López, R. Arceo, I. Cabrera-Munguia

  2. [2111.06514] - A Note On Complex Spacetime Metrics - Edward Witten

  3. [2111.06761] - Four-dimensional $\mathcal{N}=1$ SCFTs on S-folds with T-branes and AdS/CFT correspondence - Yusuke Kimura

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