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New generalized nonspherical black hole solutions
Get PDFWe present numerical evidence for the existence of several types of static black hole solutions with a nonspherical event horizon topology in d ≥ 6 spacetime dimensions. These asymptotically flat configurations are found for a specific metric ansatz and can be viewed as higher dimensional counterparts of the d = 5 static black rings, dirings and black Saturn. Similar to that case, they are supported against collapse by conical singularities. The issue of rotating generalizations of these solutions is also considered
Scalar hairy black holes and solitons in a gravitating Goldstone model
Get PDFWe study black hole solutions of Einstein gravity coupled to a specific global symmetry breaking Goldstone model described by an O(3) isovector scalar field in four spacetime dimensions. Our configurations are static and spherically symmetric, approaching at infinity a Minkowski spacetime background. A set of globally regular, particle-like solutions are found in the limit of vanishing event horizon radius. These configurations can be viewed as ’regularised’ global monopoles, since their mass is finite and the spacetime geometry has no deficit angle. As an unusual feature, we notice the existence of extremal black holes in this model defined in terms of gravity and scalar fields only
Relativistic baryons in the Skyrme model revisited
Get PDFStarting from the static Skyrme model baryon wavefunctions in their helicity eigenstates, we generalize the wavefunctions to the non-static and relativistic regime. A new representation for gamma matrices in the SU(2) collective space is constructed and the corresponding Dirac equation is obtained. Finally, we comment on possible applications of our results to the calculation of matrix elements of baryonic currents and the corresponding form factors in the relativistic case
Integrable deformations of CFTs and the discrete Hirota equations
Get PDFWe solve the discrete Hirota equations (Kirillov-Reshetikhin Q-systems) for A_r , and their analogue for D_r , for the cases where the second variable ranges over either a finite set or over all integers. Until now only special solutions were known. We find all solutions for which no component vanishes, as required in the known applications. As an introduction we present the known solution where the second variable ranges over the natural numbers
Invalidity of a strong capacity for a quantum channel with memory
Get PDFThe strong capacity of a particular channel can be interpreted as a sharp limit on the amount of information which can be transmitted reliably over that channel. To evaluate the strong capacity of a particular channel one must prove both the direct part of the channel coding theorem and the strong converse for the channel. Here we consider the strong converse theorem for the periodic quantum channel and show some rather surprising results. We first show that the strong converse does not hold in general for this channel and therefore the channel does not have a strong capacity. Instead, we find that there is a scale of capacities corresponding to error probabilities between integer multiples of the inverse of the periodicity of the channel. A similar scale also exists for the random channel
Compressibility of rotating black holes
Get PDFInterpreting the cosmological constant as a pressure, whose thermodynamically conjugate variable is a volume, modifies the first law of black hole thermodynamics. Properties of the resulting thermodynamic volume are investigated: the compressibility and the speed of sound of the black hole are derived in the case of non-positive cosmological constant. The adiabatic compressibility vanishes for a non-rotating black hole and is maximal in the extremal case - comparable with, but still less than, that of a cold neutron star. A speed of sound vs is associated with the adiabatic compressibility, which is is equal to c for a non-rotating black hole and decreases as the angular momentum is increased. An extremal black hole has v_s^2=0.9c^2 when the cosmological constant vanishes, and more generally v_s is bounded below by c/√2
Einstein-Yang-Mills-Chern-Simons solutions in D = 2n + 1 dimensions
Get PDFWe investigate finite energy solutions of the Einstein–Yang-Mills–Chern-Simons system in odd space-time dimensions, D = 2n + 1, with n > 1. Our configurations are static and spherically symmetric, approaching at infinity a Minkowski spacetime background. In contrast with the Abelian case, the contribution of the Chern-Simons term is nontrivial already in the static, spherically symmetric limit. Both globally regular, particle-like solutions and black holes are constructed numerically for several values of D. These solutions carry a nonzero electric charge and have finite mass. For globally regular solutions, the value of the electric charge is fixed by the Chern-Simons coupling constant. The black holes can be thought as non-linear superpositions of Reissner-Nordström and non-Abelian configurations. A systematic discussion of the solutions is given for D = 5, in which case the Reissner-Nordström black hole becomes unstable and develops non-Abelian hair. We show that some of these non-Abelian configurations are stable under linear, spherically symmetric perturbations. A detailed discussion of an exact D = 5 solution describing extremal black holes and solitons is also provided
Stable black hole solutions with non-Abelian fields
Get PDFWe construct finite mass, asymptotically flat black hole solutions in d = 4 Einstein– Yang-Mills theory augmented with higher order curvature terms of the gauge field. They possess non-Abelian hair in addition to Coulomb electric charge, and, below some non-zero critical temperature, they are thermodynamically preferred over the Reissner-Nordström solution. Our results indicate the existence of hairy non-Abelian black holes which are stable under linear, spherically symmetric perturbations