59390019
Can a black hole with conformal scalar hair rotate
It is shown that, under the separability assumption for the metric, the slow-rotation approximation for the Bocharova-Bronnikov-Melnikov-Bekenstein black hole in general relativity with a conformally coupled scalar field does not work outside the event horizon. Suggestions indicated by our present analysis towards a fully rotating black hole solution are discussed.
14552385
Gödel black hole, closed timelike horizon and the study of particle emissions
We show that a particle, with positive orbital angular momentum, following an outgoing null/timelike geodesic, shall never reach the closed timelike horizon present in the (4 + 1)-dimensional rotating Gödel black hole space–time. Therefore a large part of this space–time remains inaccessible to a large class of geodesic observers, depending on the conserved quantities associated with them. We discuss how this fact and the existence of the closed timelike curves present in the asymptotic region make the quantum field theoretic study of the Hawking radiation, where the asymptotic observer states are a pre-requisite, unclear. However, the semi classical approach provides an alternative to verify the Smarr formula derived recently for the rotating Gödel black hole. We present a systematic analysis of particle emissions, specifically for scalars, charged Dirac spinors and vectors, from this black hole via the semiclassical complex path method.
118343992
No hair theorems for stationary axisymmetric black holes
AbstractWe present a non-perturbative proof of the no hair theorems corresponding to scalar and Procaﬁelds for stationary axisymmetric de Sitter black hole spacetimes. Our method also applies toasymptotically ﬂat and under a reasonable assumption, to asymptotically anti-de Sitter spacetimes.Keywords: Stationary black holes, no hair theorem, de Sitter 1 Introduction The classical no hair conjecture for black holes states that any gravitational collapse reaches a ﬁnalstationary state characterized only by a small number of parameters. A part of this conjecturehas been proven rigorously by taking diﬀerent matter ﬁelds, known as the no hair theorem (seee.g. [1, 2, 3]) and deals with the uniqueness of stationary black hole solutions characterized onlyby mass, angular momentum, and charges corresponding to long range gauge ﬁelds such as theelectromagnetic ﬁeld. Any non-trivial ﬁeld conﬁguration other than the long range gauge ﬁeldspresent at the exterior of a stationary black hole is known as ‘hair’. In particular, it has beenshown that static, spherically symmetric black holes do not support hair corresponding to scalarsin convex potentials, Proca-massive vector ﬁelds [4], or even gauge ﬁelds corresponding to theAbelian Higgs model [5, 6].All the above proofs assume the spacetime to be asymptotically ﬂat, i.e., one can reach spacelikeinﬁnity so that suﬃciently rapid fall-oﬀ conditions on the matter ﬁelds can be imposed there. Butrecent observations [7, 8] suggest that there is a strong possibility that our universe is endowedwith a small but positive cosmological constant Λ. It is generally expected that in that case thespacetime in its stationary state should have an outer or cosmological Killing horizon [9]. Thecosmological Killing horizon acts in general as a causal boundary (see e.g. [10]) so that no physicalobserver can communicate beyond this horizon along a future directed path. If there is a black
118589509
A note on Hawking radiation via complex path analysis
As long as we neglect backreaction, the Hawking temperature of a given black hole would not depend upon the parameters of the particle species we are considering. In the semiclassical complex path analysis approach of Hawking radiation, this has been verified by taking scalar and Dirac spinors separately for different stationary spacetime metrics. Here we show in a coordinate-independent way that for an arbitrary spacetime with any number of dimensions, the equations of motion for a Dirac spinor, a vector, spin-2 and spin- fields reduce to Klein–Gordon equations in the WKB semiclassical limit. We then obtain, under some suitable assumptions, the complex solutions of those resulting scalar equations across the Killing horizon of a stationary spacetime to get a coordinate-independent expression for the emission probability identical for all particle species. Finally we consider some explicit examples to demonstrate the validity of that expression.
118446121
Mass function and particle creation in Schwarzschild–de Sitter spacetime
We construct a mass or energy function for the non-Nariai class Schwarzschild–de Sitter black hole spacetime in the region between the black hole and the cosmological event horizons. The mass function is local, positive definite, continuous and increases monotonically with the radial distance from the black hole event horizon. We derive the Smarr formula using this mass function, and demonstrate that the mass function reproduces the two-temperature Schwarzschild–de Sitter black hole thermodynamics, along with a term corresponding to the negative pressure due to positive cosmological constant. We further give a field theoretic derivation of the particle creation by both the horizons and discuss its connection with the mass function.
12947810
Effect of a positive cosmological constant on cosmic strings
We study cosmic Nielsen-Olesen strings in space-times with a positive cosmological constant. For the free cosmic string in a cylindrically symmetric space-time, we calculate the contribution of the cosmological constant to the angle deficit, and to the bending of null geodesics. For a cosmic string in a Schwarzschild-de Sitter space-time, we use Kruskal patches around the inner and outer horizons to show that a thin string can pierce them.
119096880
Constraints on Two-Component Dark Matter
We study 'Higgs Portal' 2-component Dark Matter scenario with two interacting cold Dark Matter (DM) candidates: a neutral scalar singlet ($\varphi$) and a neutral Majorana fermion ($\nu$). The relic abundance of $\varphi$ and $\nu$ is found assuming thermal DM production and solving the Boltzmann equations. We scan over the parameter space of the model to determine regions consistent with the WMAP data for DM relic abundance and the XENON100 direct detection limits for the DM-nucleus cross section.
15636466
Gaugino mass nonuniversality in an SO(10) supersymmetric grand unified theory: Low-energy spectra and collider signals
We derive the nonuniversal gaugino mass ratios in a supergravity (SUGRA) framework where the Higgs superfields belong to the nonsinglet representations 54 and 770 in an SO(10) grand unified theory (GUT). We evaluate the ratios for the phenomenologically viable intermediate breaking chain SU(4){sub C}xSU(2){sub L}xSU(2){sub R}(G{sub 422}). After a full calculation of the gaugino mass ratios, noting some errors in the earlier calculation for 54, we obtain, using the renormalization group equations, interesting low scale phenomenology of such breaking patterns. Here, we assume the breaking of the SO(10) GUT group to the intermediate gauge group and that to the standard model take place at the GUT scale itself. We also study the collider signatures in multilepton channels at the Large Hadron Collider (LHC) for some selected benchmark points allowed by the cold dark-matter relic density constraint provided by the WMAP data and compare these results with the minimal supergravity (mSUGRA) framework with similar gluino masses indicating their distinguishability in this regard.
119303787
Dark vector-gauge-boson model
A model based on $SU(3{)}_{C}\ifmmode\times\else\texttimes\fi{}SU(2{)}_{L}\ifmmode\times\else\texttimes\fi{}U(1{)}_{Y}\ifmmode\times\else\texttimes\fi{}SU(2{)}_{N}$ has recently been proposed, where the $SU(2{)}_{N}$ vector gauge bosons are neutral, so that a vector dark-matter candidate is possible and constrained by data to be less than about 1 TeV. We explore further implications of this model, including a detailed study of its Higgs sector. We improve on its dark-matter phenomenology, as well as its discovery reach at the Large Hadron Collider.
10436358
Nonuniversal scalar mass scenario with Higgs funnel region of supersymmetric dark matter: A signal-based analysis for the Large Hadron Collider
We perform a multilepton channel analysis in the context of the Large Hadron Collider (LHC) for Wilkinson Microwave Anisotropy probe (WMAP) compatible points in a model with non-universal scalar masses, which admits a Higgs funnel region of supersymmetry dark matter even for a small tan�. In addition to two and threelepton final states, four-lepton events, too, are shown to be useful for this purpose. We also compare the collider signatures in similar channels for WMAP compatible points in the minimal supergravity (mSUGRA) framework with similar gluino masses. Some definite features of such non-universal scenario emerge from the analysis.
14408151
Signatures of non‐universal gaugino and scalar masses at the Large Hadron Collider (LHC)
We perform a multichannel analysis in context of the Large Hadron Collider (LHC) for supersymmetric (SUSY) theories with high-scale non-universal gaugino masses arising from different non-singlet representations of SU(5) and SO(10) gauge groups in a SUSY-GUT scenario and non-universal scalar masses in form of squark-slepton non-universality, third family scalar non-universality and that arising due to SO(10) D-terms. We present the numerical predictions over a wide region of parameter space using event generator Pythia. Certain broad features emerge from the study which may be useful to identify these non-universal schemes and distinguish them from the minimal supergravity (mSUGRA) framework.