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We investigate the evaporation process of a Kerr–de Sitter black hole with the Unruh–Hawking-like vacuum state, which is a realistic vacuum state modelling the evaporation process of a black hole originating from gravitational collapse. We also compute the greybody factors for gravitons, photons, and conformal-coupling massless scalar particles by using the analytic solutions of the Teukolsky equation in the Kerr–de Sitter background. It turns out that the cosmological constant quenches the amplification factor and it approaches to zero towards the critical point where the Nariai and extremal limits merge together. We confirm that even near the critical point, the superradiance of gravitons is more significant than that of photons and scalar particles. Angular momentum is carried out by particles several times faster than the mass energy decreases. This means that a Kerr–de Sitter black hole rapidly spins down to a nearly Schwarzschild–de Sitter black hole before it completely evaporates. We also compute the time evolution of the Bekenstein–Hawking entropy. The total entropy of the Kerr–de Sitter black hole and cosmological horizon increases with time, which is consistent with the generalized second law of thermodynamics. [ABSTRACT FROM AUTHOR]

We examine the effect of large extra dimensions on vacuum decay in the Randall–Sundrum (RS) braneworld paradigm. We assume the scalar field is confined to the brane, and compute the probability for forming an "anti-de Sitter" (AdS) bubble inside a critical flat RS brane. We present the first full numerical solutions for the brane instanton considering two test potentials for the scalar field. We explore the geometrical impact of thin and thick bubble walls, and compute the instanton action in a range of cases. We conclude by commenting on a more physically realistic potential relevant for the Standard Model Higgs. For bubbles with large backreaction, the extra dimension has a dramatic effect on the tunnelling rate, however, for the weakly backreacting bubbles more relevant for realistic Standard Model potentials, the extra dimension has little impact. [ABSTRACT FROM AUTHOR]

Abstract We study the gravitational collapse of axion dark matter in null coordinates, assuming spherical symmetry. Compared with previous studies, we use a simpler numerical scheme which can run, for relevant parameters, in a few minutes or less on a desktop computer. We use it to accurately determine the domains of parameter space in which the axion field forms a black hole, an axion star or a relativistic Bosenova. [ABSTRACT FROM AUTHOR]

In the absence of new physics around $$10^{10}$$ GeV, the electroweak vacuum is at best metastable. This represents a major challenge for high scale inflationary models as, during the early rapid expansion of the universe, it seems difficult to understand how the Higgs vacuum would not decay to the true lower vacuum of the theory with catastrophic consequences if inflation took place at a scale above $$10^{10}$$ GeV. In this paper we show that the non-minimal coupling of the Higgs boson to curvature could solve this problem by generating a direct coupling of the Higgs boson to the inflationary potential thereby stabilizing the electroweak vacuum. For specific values of the Higgs field initial condition and of its non-minimal coupling, inflation can drive the Higgs field to the electroweak vacuum quickly during inflation. [ABSTRACT FROM AUTHOR]

The discovery of the Standard Model Higgs boson opens up a range of speculative cosmological scenarios, from the formation of structure in the early universe immediately after the big bang, to relics from the electroweak phase transition one nanosecond after the big bang, on to the end of the present-day universe through vacuum decay. Higgs physics is wide ranging, and gives an impetus to go beyond the Standard Models of particle physics and cosmology to explore the physics of ultra-high energies and quantum gravity. [ABSTRACT FROM PUBLISHER]

In the context of quantum field theory, an anomaly exists when a theory has a classical symmetry which is not a symmetry of the quantum theory. This short exposition aims at introducing a new point of view, which is that the proper setting for anomaly calculations is the 'in-in', or closed-time path formulation of quantum field theory. There are also some new results for anomalies in the context of boundary value problems, and a new correction to the a5 heat-kernel coefficient. This article is part of a special issue of Journal of Physics A:Mathematical and Theoretical in honour of StuartDowker's 75th birthday devoted to 'Applications of zeta functions and other spectral functions in mathematics and physics'. [ABSTRACT FROM AUTHOR]

Abstract: Moduli stabilisation is explored in the context of low-energy heterotic M-theory to show that a small value of the cosmological constant can result from a balance between the negative potential energy left over from stabilising the moduli and a positive Casimir energy from the higher dimensions. Supersymmetry breaking is induced by the fermion boundary conditions on the two branes in the theory. An explicit calculation of the Casimir energy for the gravitino reveals that the energy has the correct sign, although the size of the contribution is close to the edge of the parameter range for which the calculation is valid. [Copyright &y& Elsevier]

Abstract: This Letter considers anomaly cancellation for eleven-dimensional supergravity on a manifold with boundary and theories related to heterotic M-theory. The Green–Schwartz mechanism is implemented without introducing distributions. The importance of the supersymmetry anomaly in constructing the low energy action is discussed and it is argued that a recently proposed action for low-energy heterotic M-theory gives a supersymmetric theory to all orders in the gravitational coupling κ. [Copyright &y& Elsevier]

Abstract: This paper considers eleven-dimensional supergravity on a manifold with boundary and the theories related to low energy heterotic M-theory, in which the matter is confined to the boundary. New low energy actions and boundary conditions on supergravity fields are derived. Previous problems with infinite constants in the action are overcome. The new boundary conditions are shown to be consistent with supersymmetry, and their role in the ten-dimensional reduction and gaugino condensation is briefly discussed. [Copyright &y& Elsevier]

Abstract: In brane world scenarios, inflationary vacuum energy may escape into the higher-dimensional bulk, leaving behind a dark radiation effect on the brane. This Letter analyses the damping of an inflaton by massless bulk scalar radiation and the production of dark radiation in a Randall–Sundrum type of model. [Copyright &y& Elsevier]

We discuss the spectrum of scalar density perturbations from warm inflation when the friction coefficient Γ in the inflaton equation is dependent on the inflaton field. The spectral index of scalar fluctuations depends on a new slow-roll parameter constructed from Γ. A numerical integration of the perturbation equations is performed for a model of warm inflation and gives a good fit to the WMAP data for reasonable values of the model''s parameters. [Copyright &y& Elsevier]

A new action for eleven-dimensional supergravity on a manifold with boundary is presented. The action is a possible low energy limit of M-theory. Previous problems with infinite constants in the action are overcome and a new set of boundary conditions relating the behaviour of the supergravity fields to matter fields are obtained. One effect of these boundary conditions is that matter fields generate gravitational torsion. [Copyright &y& Elsevier]

Abstract: Recent time-of-flight measurements on muon neutrinos in the OPERA neutrino oscillation experiment have found anomalously short times compared to the light travel-times, corresponding to a superluminal velocity, v −1=2.37±0.32×10−5 in units where c =1. We show that cosmological bounds rule out an explanation involving a Lorentz invariant tachyonic neutrino. At the OPERA energy scale, nucleosynthesis constraints imply v −1<0.86×10−12 and the Cosmic Microwave Background observations imply v −1<7.1×10−23. The CMB limit on the velocity of a tachyon with an energy of 10MeV is stronger than the SN 1987A limit. Superluminal neutrinos that could conceivably be observed at particle accelerator energy scales would have to be associated with Lorentz symmetry violation. [Copyright &y& Elsevier]

We discuss the effect of gravitational interactions on the lifetime of the Higgs vacuum where generic quantum gravity corrections are taken into account. Using a "thin-wall" approximation, we provide a proof of principle that small black holes can act as seeds for vacuum decay, spontaneously nucleating a new Higgs phase centered on the black hole with a lifetime measured in millions of Planck times rather than billions of years. The corresponding parameter space constraints are, however, extremely stringent; therefore, we also present numerical evidence suggesting that with thick walls, the parameter space may open up. Implications for collider black holes are discussed. [ABSTRACT FROM AUTHOR]