| 1. |
- Ananth, Sudarshan, et al.
(author)
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Maximal supergravity and the quest for finiteness
- 2018
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In: International Journal of Modern Physics D. - 0218-2718. ; 27:14
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Research review (peer-reviewed)abstract
- We show that N = 8 supergravity may possess an even larger symmetry than previously believed. Such an enhanced symmetry is needed to explain why this theory of gravity exhibits ultraviolet behavior reminiscent of the finite N = 4 Yang-Mills theory. We describe a series of three steps that leads us to this result.
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| 2. |
- Banerjee, Souvik, et al.
(author)
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Curing with Hemlock : Escaping the swampland using instabilities from string theory
- 2021
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In: International Journal of Modern Physics D. - : World Scientific. - 0218-2718. ; 30:14
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Journal article (peer-reviewed)abstract
- In this essay, we will take a wonderful ride on a dark bubble with strings attached, which carries our universe out of the swampland and makes it realizable in the landscape of string theory. To find the way to the landscape, we make use of apparently hostile corners of the swampland and their instabilities.
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| 3. |
- Beltran Jimenez, Jose, et al.
(author)
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The canonical frame of purified gravity
- 2019
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In: International Journal of Modern Physics D. - : World Scientific Publishing Co. Pte Ltd. - 0218-2718. ; 28:14
-
Journal article (peer-reviewed)abstract
- In the recently introduced gauge theory of translations, dubbed Coincident General Relativity (CGR), gravity is described with neither torsion nor curvature in the spacetime affine geometry. The action of the theory enjoys an enhanced symmetry and avoids the second derivatives that appear in the conventional Einstein-Hilbert action. While it implies the equivalent classical dynamics, the improved action principle can make a difference in considerations of energetics, thermodynamics and quantum theory. This paper reports on possible progress in those three aspects of gravity theory. In the so-called purified gravity, (1) energy-momentum is described locally by a conserved, symmetric tensor, (2) the Euclidean path integral is convergent without the addition of boundary or regulating terms and (3) it is possible to identify a canonical frame for quantization.
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| 4. |
- Burigana, Carlo, et al.
(author)
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Recent results and perspectives on cosmology and fundamental physics from microwave surveys
- 2016
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In: International Journal of Modern Physics D. - 0218-2718. ; 25:6
-
Research review (peer-reviewed)abstract
- Recent cosmic microwave background (CMB) data in temperature and polarization have reached high precision in estimating all the parameters that describe the current so-called standard cosmological model. Recent results about the integrated Sachs-Wolfe (ISW) effect from CMB anisotropies, galaxy surveys, and their cross-correlations are presented. Looking at fine signatures in the CMB, such as the lack of power at low multipoles, the primordial power spectrum (PPS) and the bounds on non-Gaussianities, complemented by galaxy surveys, we discuss inflationary physics and the generation of primordial perturbations in the early universe. Three important topics in particle physics, the bounds on neutrinos masses and parameters, on thermal axion mass and on the neutron lifetime derived from cosmological data are reviewed, with attention to the comparison with laboratory experiment results. Recent results from cosmic polarization rotation (CPR) analyses aimed at testing the Einstein equivalence principle (EEP) are presented. Finally, we discuss the perspectives of next radio facilities for the improvement of the analysis of future CMB spectral distortion experiments.
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| 5. |
- Chen, Pisin, et al.
(author)
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Unclothed firewalls
- 2016
-
In: International Journal of Modern Physics D. - : World Scientific Publishing. - 0218-2718. ; 25:13
-
Journal article (peer-reviewed)abstract
- We have previously argued that fluctuations of the Hawking emission rate can cause a black hole event horizon to fluctuate inside the location of a putative firewall, rendering the firewall naked. This assumes that the firewall is located near where the horizon would be expected based on the past evolution of the spacetime. Here, we expand our previous results by defining two new estimates for where the firewall might be that have more smooth temporal behavior than our original estimate. Our results continue to contradict the usual assumption that the firewall should not be observable except by infalling observers. This casts doubt about the idea that firewalls are the 'most conservative' solution to the information loss paradox.
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| 6. |
- Danielsson, Ulf, et al.
(author)
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What if string theory has no de Sitter vacua?
- 2018
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In: International Journal of Modern Physics D. - : WORLD SCIENTIFIC PUBL CO PTE LTD. - 0218-2718. ; 27:12
-
Research review (peer-reviewed)abstract
- We present a brief overview of attempts to construct de Sitter vacua in string theory and explain how the results of this 20-year endeavor could point to the fact that string theory harbors no de Sitter vacua at all. Making such a statement is often considered controversial and "bad news for string theory". We discuss how perhaps the opposite can be true.
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| 7. |
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| 8. |
- Freese, Katherine
(author)
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Status of dark matter in the universe
- 2017
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In: International Journal of Modern Physics D. - 0218-2718. ; 26:6
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Research review (peer-reviewed)abstract
- Over the past few decades, a consensus picture has emerged in which roughly a quarter of the universe consists of dark matter. I begin with a review of the observational evidence for the existence of dark matter: rotation curves of galaxies, gravitational lensing measurements, hot gas in clusters, galaxy formation, primordial nucleosynthesis and Cosmic Microwave Background (CMB) observations. Then, I discuss a number of anomalous signals in a variety of data sets that may point to discovery, though all of them are controversial. The annual modulation in the DAMA detector and/or the gamma-ray excess seen in the Fermi Gamma Ray Space Telescope from the Galactic Center could be due to WIMPs; a 3.5 keV X-ray line from multiple sources could be due to sterile neutrinos; or the 511 keV line in INTEGRAL data could be due to MeV dark matter. All of these would require further confirmation in other experiments or data sets to be proven correct. In addition, a new line of research on dark stars is presented, which suggests that the first stars to exist in the universe were powered by dark matter heating rather than by fusion: the observational possibility of discovering dark matter in this way is discussed.
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| 9. |
- Garny, Mathias, et al.
(author)
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Signatures of Majorana dark matter with t-channel mediators
- 2015
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In: International Journal of Modern Physics D. - 0218-2718. ; 24:7
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Journal article (peer-reviewed)abstract
- Three main strategies are being pursued to search for nongravitational dark matter signals: direct detection, indirect detection and collider searches. Interestingly, experiments have reached sensitivities in these three search strategies which may allow detection in the near future. In order to take full benefit of the wealth of experimental data, and in order to confirm a possible dark matter signal, it is necessary to specify the nature of the dark matter particle and of the mediator to the Standard Model. In this paper, we focus on a simplified model where the dark matter particle is a Majorana fermion that couples to a light Standard Model fermion via a Yukawa coupling with a scalar mediator. We review the observational signatures of this model and we discuss the complementarity among the various search strategies, with emphasis in the well motivated scenario where the dark matter particles are produced in the early universe via thermal freeze-out.
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| 10. |
- Grumiller, Daniel, 1973-, et al.
(author)
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Consistent boundary conditions for cosmological topologically massive gravity at the chiral point
- 2008
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In: International Journal of Modern Physics D. - 0218-2718. ; 17:13-14, s. 2367-2372
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Journal article (peer-reviewed)abstract
- We show that cosmological topologically massive gravity at the chiral point allows not only Brown-Henneaux boundary conditions as consistent boundary conditions, but slightly more general ones which encompass the logarithmic primary found in 0805.2610 as well as all its descendants.
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