M-theory branes: U-duality properties and a class of new static solutions

Rama, S. Kalyana

doi:10.1103/physrevd.88.044007

Cited by 5 publications

(6 citation statements)

References 69 publications

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“…It is possible to observe γ-rays from regions with high DM densities using high precision detectors, such as the space-borne γ-ray detector Fermi Large Area Telescope (Fermi-LAT) [5]. Many studies have been performed to probe the DM signatures in the Fermi-LAT data from large astrophysical systems, such as the Galactic halo [6][7][8][9][10][11][12], galaxy clusters [13], and Galactic DM substructures [14][15][16]. However, the contribution of DM annihilation to the reported GeV γ− rays has not been confirmed [8,[17][18][19][20][21][22][23][24][25][26][27][28][29].…”

Section: Introductionmentioning

confidence: 99%

Searching for γ -ray emission from Reticulum II by Fermi-LAT

Zhao

Yin

et al. 2018

Chinese Phys. C

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Recently, many new dwarf spheroidal satellites (dSphs) have been discovered by the Dark Energy Survey (DES). These dSphs are ideal candidates for probing for gamma-ray emissions from dark matter (DM) annihilation. However, no significant signature has been found by the Fermi-LAT dSph observations. In this work, we reanalyze the Fermi-LAT Pass 8 data from the direction of Reticulum II, where a slight excess has been reported by some previous studies. We treat Reticulum II (DES J0335.6-5403) as a spatially extended source, and find that no significant gamma-ray signature is observed. Based on this result, we set upper-limits on the DM annihilation cross section.

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Section: Introductionmentioning

confidence: 99%

Searching for γ -ray emission from Reticulum II by Fermi-LAT

Zhao

Yin

et al. 2018

Chinese Phys. C

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“…We use the un-binned analysis method, which is similar to the one described in Ackermann et al (2013), to search for the line signal at different energies. The likelihood is described as…”

Section: Numerical Resultsmentioning

confidence: 99%

“…Since such a 130 GeV γ-ray line signal consists of only ∼ 14 photons, the imperfect consistency of these photons with the expected DM distribution can just be due to the limited statistics (Yang et al 2012). However, no firm evidence for the 130 GeV γ-ray line emission has been found by the Fermi-LAT collaboration (Ackermann et al 2013). Such a negative result is slightly disappointing.…”

Section: Introductionmentioning

confidence: 99%

The spatial distribution of dark matter annihilation originating from a gamma-ray line signal

Dong

2014

Res. Astron. Astrophys.

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The GeV−TeV γ−ray line signal is the smoking gun signature of the dark matter annihilation or decay. The detection of such a signal is one of the main targets of some space-based telescopes, including Fermi-LAT and the upcoming CALET, DAMPE and Gamma-400. An important feature of the dark-matter-annihilation originated γ−ray line photons is their concentration at the center of the Galaxy. So far no reliable γ−ray line has been detected by Fermi-LAT and the upper limits on the cross section of annihilation into γ−rays have been reported. We use these upper limits to estimate the "maximal" number of γ−ray line photons detectable for Fermi-LAT, DAMPE and Gamma-400 and then investigate the spatial distribution of these photons. We show that usually the center of the distribution region will be offset from the Galactic centre (Sgr A ⋆ ) due to the limited statistics. Such a result is almost independent of the dark matter distribution models and renders the reconstruction of the dark matter distribution with the γ−ray line signal very challenging for the foreseeable space-based detectors.

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“…From a string theory perspective, it has been proposed that stable states of intersecting brane configurations can give rise to singularity-free quantumfuzzball solutions [10]. Horizonless solutions that appear as black holes at large distances can be constructed from a variety of brane configurations [11][12][13][14]. However, here we shall just consider gravity at the classical level and examine the possibility of arbitrarily compact horizonless singularity-free solutions.…”

Section: Introductionmentioning

confidence: 99%

Horizonless, singularity-free, compact shells satisfying NEC

Shankar

2017

Gen Relativ Gravit

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Gravitational collapse singularities are undesirable, yet inevitable to a large extent in General Relativity. When matter satisfying null energy condition (NEC) collapses to the extent a closed trapped surface is formed, a singularity is inevitable according to Penrose's singularity theorem. Since positive mass vacuum solutions are generally black holes with trapped surfaces inside the event horizon, matter cannot collapse to an arbitrarily small size without generating a singularity. However, in modified theories of gravity where positive mass vacuum solutions are naked singularities with no trapped surfaces, it is reasonable to expect that matter can collapse to an arbitrarily small size without generating a singularity. Here we examine this possibility in the context of a modified theory of gravity with torsion in an extra dimension. We study singularity-free static shell solutions to evaluate the validity of NEC on the shell. We find that with sufficiently high pressure, matter can be collapsed to arbitrarily small size without violating NEC and without producing a singularity.

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M-theory branes: U-duality properties and a class of new static solutions

Cited by 5 publications

References 69 publications

Searching for γ -ray emission from Reticulum II by Fermi-LAT

Searching for γ -ray emission from Reticulum II by Fermi-LAT

The spatial distribution of dark matter annihilation originating from a gamma-ray line signal

Horizonless, singularity-free, compact shells satisfying NEC

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