703 research outputs found
Existence Theorems for Hairy Black Holes in su(N) Einstein-Yang-Mills theories
We establish the existence of hairy black holes in su(N) Einstein-Yang-Mills
theories, described by N-1 parameters, corresponding to the nodes of the gauge
field functions.Comment: 64 pages, latex2e, minor changes on the nature of the parameters,
version to appear in J. Math. Phy
Instability of hairy black holes in spontaneously-broken Einstein-Yang-Mills-Higgs systems
The stability of a new class of hairy black hole solutions in the coupled
system of Einstein-Yang-Mills-Higgs is examined, generalising a method
suggested by Brodbeck and Straumann and collaborators, and Volkov and Gal'tsov.
The method maps the algebraic system of linearised radial perturbations of the
various field modes around the black hole solution into a coupled system of
radial equations of Schr\"odinger type. No detailed knowledge of the black hole
solution is required, except from the fact that the boundary conditions at the
physical space-time boundaries (horizons) must be such so as to guarantee the
{\it finiteness} of the various expressions involved. In this way, it is
demonstrated that the above Schr\"odinger equations have bound states, which
implies the instability of the associated black hole solution.Comment: 8 pages, LATE
Monopole Black Hole Skyrmions
Charged black hole solutions with pion hair are discussed. These can be used
to study monopole black hole catalysis of proton decay. There also exist multi-
black hole skyrmion solutions with BPS monopole behavior.Comment: 16 pages including 6 figure
Quantum Decoherence in a Four-Dimensional Black Hole Background
We display a logarithmic divergence in the density matrix of a scalar field
in the presence of an Einstein-Yang-Mills black hole in four dimensions. This
divergence is related to a previously-found logarithmic divergence in the
entropy of the scalar field, which cannot be absorbed into a renormalization of
the Hawking-Bekenstein entropy of the black hole. As the latter decays, the
logarithmic divergence induces a non-commutator term \nd{\delta H}\rho in the
quantum Liouville equation for the density matrix of the scalar field,
leading to quantum decoherence. The order of magnitude of \nd{\delta H} is
, where is the mass of the scalar particle.Comment: 13-pages LATE
On the Existence of Soliton and Hairy Black Hole Solutions of su(N) Einstein-Yang-Mills Theory with a Negative Cosmological Constant
We study the existence of soliton and black hole solutions of four-dimensional Einstein–Yang–Mills theory with a negative cosmological constant. We prove the existence of non-trivial solutions for any integer N, with N − 1 gauge field degrees of freedom. In particular, we prove the existence of solutions in which all the gauge field functions have no zeros. For fixed values of the parameters (at the origin or event horizon, as applicable) defining the soliton or black hole solutions, if the magnitude of the cosmological constant is sufficiently large, then the gauge field functions all have no zeros. These latter solutions are of special interest because at least some of them will be linearly stable
Higher-dimensional solitons and black holes with a non-minimally coupled scalar field
We study higher-dimensional soliton and hairy black hole solutions of the
Einstein equations non-minimally coupled to a scalar field. The scalar field
has no self-interaction potential but a cosmological constant is included.
Non-trivial solutions exist only when the cosmological constant is negative and
the constant governing the coupling of the scalar field to the Ricci scalar
curvature is positive. At least some of these solutions are stable when this
coupling constant is not too large.Comment: 17 pages, revtex4, 21 figures, minor changes to match published
versio
Understanding temporal rhythms and travel behaviour at destinations: Potential ways to achieve more sustainable travel
This paper analyses the roles played by time in destination-based travel behaviour. It contrasts clock time's linear view of time with fragmented time, instantaneous time, fluid time and flow, time out and the multiple temporalities of tourism experiences. It explores temporal issues in a destination travel context, using qualitative techniques. Data were captured using diary photography, diary-interview method with tourists at a rural destination; their spatial and temporal patterns were captured using a purpose built smartphone app. The analysis revealed three temporal themes influencing travel behaviour: time fluidity; daily and place-related rhythms; and control of time. Three key messages emerge for future sustainable tourist destination-based travel systems. Given the strong desire for temporal fluidity, transport systems should evolve beyond clock-time regimes. Second, temporal forces favour personal modes of transport (car, walk, cycle), especially in rural areas where public transport cannot offer flexibility. Third, the car is personalised and perceived to optimise travel fluidity and speed, but is currently unsustainable. Imaginative initiatives, using new mobile media technology can offer new positive and proactive car travel, utilising spare public and private vehicle capacity. Research is needed to implement mechanisms for individualised space-time scheduling and collective vehicle use strategies. © 2013 Copyright Taylor and Francis Group, LLC
Case Study: Cancrum oris (noma) in a malnourished HIV-positive child from rural Kwazulu-Natal
Cancrum oris (noma – derived from the Greek nomein, ‘to devour\') is an infectious disease with a fulminating course that destroys the oro-facial tissues and other neighbouring structures.1 Although cancrum oris can occur at any age, it is most commonly in malnourished children between the ages of 1 and 5 years whose general health has been further weakened by some infectious disease, usually measles but also tuberculosis, gastro-enteritis, typhoid, whooping cough, or malignant disease such as leukaemia. The possible relevance to HIV has not been fully investigated. This report details a case presenting to East Griqualand and Usher Memorial Hospital, Kokstad, KwaZulu-Natal.
Southern African Journal of HIV Medicine Vol. 5 (3) 2004: 45-4
Regular and Black Hole Solutions in the Einstein-Skyrme Theory with Negative Cosmological Constant
We study spherically symmetric regular and black hole solutions in the
Einstein-Skyrme theory with a negative cosmological constant. The Skyrme field
configuration depends on the value of the cosmological constant in a similar
manner to effectively varying the gravitational constant. We find the maximum
value of the cosmological constant above which there exists no solution. The
properties of the solutions are discussed in comparison with the asymptotically
flat solutions. The stability is investigated in detail by solving the linearly
perturbed equation numerically. We show that there exists a critical value of
the cosmological constant above which the solution in the branch representing
unstable configuration in the asymptotically flat spacetime turns to be
linearly stable.Comment: 10 pages, 9 figures, comments and one reference added, to appear in
Class.Quant.Gra
Lorentz and CPT Invariance Violation In High-Energy Neutrinos
High-energy neutrino astronomy will be capable of observing particles at both
extremely high energies and over extremely long baselines. These features make
such experiments highly sensitive to the effects of CPT and Lorentz violation.
In this article, we review the theoretical foundation and motivation for CPT
and Lorentz violating effects, and then go on to discuss the related
phenomenology within the neutrino sector. We describe several signatures which
might be used to identify the presence of CPT or Lorentz violation in next
generation neutrino telescopes and cosmic ray experiments. In many cases,
high-energy neutrino experiments can test for CPT and Lorentz violation effects
with much greater precision than other techniques.Comment: 27 pages, 8 figure
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