Natural explanation for 130 GeV photon line within vector boson dark matter model

We present a dark matter model for explaining the observed 130 GeV photon line from the galaxy center. The dark matter candidate is a vector boson of mass $m_V$ with a dimensionless coupling to the photon and $Z$ boson. The model predicts a double line photon spectrum at energies equal to $m_V$ and $m_V(1-m_Z^2/4m_V^2)$ originating from the dark matter annihilation. The same coupling leads to a mono-photon plus missing energy signal at the LHC. The entire perturbative parameter space can be probed by the 14 TeV LHC run. The model has also a good prospect of being probed by direct dark matter searches as well as the measurement of the rates of $h \to \gamma \gamma$ and $h \to Z \gamma$ at the LHC.Comment: 11 pages,4 figures,Discussion of the generalized Chern-Simons term is adde

Higgs Inflation and General Initial Conditions

Higgs field of particle physics can play the role of the inflaton in the early universe, if it is non-minimally coupled to gravity. The Higgs inflation scenario predicts a small tensor to scalar ratio: $r\simeq 0.003$. Although this value is consistent with the upper bound $r < 0.12$ given by BICEP2/Keck Array and Planck data, but it is not at their maximum likelihood point: $r\simeq 0.05$. Inflationary observables depend not only on the inflationary models, but also depend on the initial conditions of inflation. Changing initial state of inflation can improve the value of $r$. In this work, we study the Higgs inflation model under general initial conditions and show that there is a subset of these general initial conditions which leads to enhancement of $r$. Then we show that this region of parameter space is consistent with non-Gaussianity bound.Comment: 13 pages, 2 figure

Tachyon Inflation in Teleparallel Gravity

We present a tachyonic field inflationary model in a teleparallel framework. We show that tachyonic coupled with the f(T) gravity model can describe the inflation era in which f(T) is an arbitrary function of torsion scalar T. For this purpose, dynamical behavior of the tachyonic field in different potentials is studied, it is shown that the tachyonic field with these potentials can be an effective candidate for inflation. Then, we discuss slow-roll conditions and show that by the appropriate choice of the parameters, the inflation era can be explained via this model. Finally, we argue that our model not only satisfies the result of BICEP2, Keck Array and Plank for the upper limit of $r < .012$ but also, the obtained value for spectral index $n_{s}$ is compatible with the results of Plank and also Plank + WMAP + HighL + BAO at the 68% confidence level.Comment: 15 pages, 5 figure

Dynamical non-locality in the near-horizon region of a black hole with quantum time

The formalization of the modular energy operator within the curved spacetime is achieved through the timeless approach proposed by Page and Wootters. The investigation is motivated by the peculiar behavior of the near horizon region of a black hole and its quantum effects, leading to a restriction of the study to the immediate vicinity. The focus lies on the perspective of a static observer positioned close to the horizon. This paper highlights the alteration of the modular energy's behavior in this region compared to flat spacetime. Furthermore, it is observed that the geometry of the spacetime influences the non-local properties of the modular energy. Moreover, within the event horizon of the black hole, the modular energy exhibits a completely distinct behavior, rendering its modular behavior imperceptible in this specific region

Cosmological Study in F(R,T)F(R, T) Quasi-dilaton Massive Gravity

This study explores the cosmological implications of the $F(R, T)$ quasi-dilaton massive gravity theory, a modification of the de Rham-Gabadadze-Tolley (dRGT) massive gravity theory. Our analysis focuses on the self-accelerating solution of the background equations of motion, which are shown to exist in the theory. Notably, we find that the theory features an effective cosmological constant, which has important implications for our understanding of the universe's accelerated expansion. To test the viability of the $F(R, T)$ quasi-dilaton massive gravity theory, we utilize the Union2 Type Ia Supernovae (SNIa) dataset, comprising 557 observations. Our results demonstrate that the theory is capable of explaining the accelerated expansion of the universe without requiring the presence of dark energy. This finding supports the potential of the $F(R, T)$ quasi-dilaton massive gravity theory as an alternative explanation for the observed cosmic acceleration. Moreover, we investigate the properties of tensor perturbations within the framework of this theory and derive a novel expression for the dispersion relation of gravitational waves. Our analysis reveals interesting features of the modified dispersion relation in the Friedmann-Lema\^itre-Robertson-Walker cosmology, providing new insights into the nature of gravitational waves in the contest of the $F(R, T)$ quasi-dilaton massive gravity theory

Massive gravity solution of Black Holes and Entropy Bounds

The dRGT massive gravity represent a comprehensive theory which properly describes massive graviton field. Latterly, the exact spherical solutions are identified for the black hole in the dRGT massive gravity theory. In this paper, we derive Bousso's D-bound entropy for the black hole solutions of dRGT massive gravity. By an entropic consideration which provides a criterion, it is demonstrated that the relation between the D-bound and Bekenstein entropy bound imposes some constraints on the structure parameters of black hole solutions in dRGT massive gravity.Comment: 17 page

Cosmology of Dirac-Born-Infeld dRGT massive gravity

We introduce the cosmological analysis of the Dirac-Born-Infeld dRGT massive gravity theory which is a new extension of de Rham-Gabadadze-Tolley (dRGT) massive gravity. In this theory, we consider the Dirac-Born-Infeld (DBI) scalar field which is coupled to the graviton field. Moreover, we perform the cosmological background equations, and we demonstrate the self-accelerating background solutions. We show that the theory consists of self-accelerating solutions with an effective cosmological constant. In the following, we exhibit tensor perturbations analyses and achieve the dispersion relation of gravitational waves. We analyze the propagation of gravitational perturbation in the Friedmann-Lema\^itre-Robertson-Walker cosmology in the DBI dRGT massive gravity. Finally, we present the vector and scalar perturbations to show the stability conditions of the theory.Comment: arXiv admin note: text overlap with arXiv:2204.0559