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pro vyhledávání: '"Copsey, Keith"'
Autor:
Copsey, Keith
Negative mass brane-like objects known as orientifolds are crucial in the construction of all presently understood realistic string compactifications and I review in general the link between negative energy objects and the existence of a landscape of
Externí odkaz:
http://arxiv.org/abs/1303.4791
Autor:
Copsey, Keith, Mann, Robert
We examine spacetimes which generalize Lifshitz scaling to allow hyperscaling violation invariance (i.e. a constant conformal transformation) for the types of singularities frequently found in the Lifshitz case. We find that most of these spacetimes
Externí odkaz:
http://arxiv.org/abs/1210.1231
Autor:
Copsey, Keith, Mann, Robert B.
We point out that the metrics recently proposed by K. Balasubramanian and J. McGreevy \cite{BalaMcGreevyLifshitz} as gravitational duals to Lifshitz Chern-Simons gauge theories contain both a hidden null singularity and a region of closed timelike cu
Externí odkaz:
http://arxiv.org/abs/1112.0578
Autor:
Copsey, Keith
I point out that the usual Coleman-de Luccia analysis of tunnelling via instantons between perturbatively stable minima using the thin-wall approximation misses one of the effects of gravitational backreaction on the on-shell action and hence the dec
Externí odkaz:
http://arxiv.org/abs/1109.4931
Autor:
Copsey, Keith
I provide some simple physical arguments that, once gravitation and some subtleties are taken into account, rather broad classes of potentials result in instantons which tunnel relatively rapidly between perturbatively stable minima. In particular, d
Externí odkaz:
http://arxiv.org/abs/1108.2255
Autor:
Copsey, Keith, Mann, Robert
Publikováno v:
JHEP 1103:039,2011
There has been significant interest in the last several years in studying possible gravitational duals, known as Lifshitz spacetimes, to anisotropically scaling field theories by adding matter to distort the asymptotics of an AdS spacetime. We point
Externí odkaz:
http://arxiv.org/abs/1011.3502
Autor:
Copsey, Keith, Mann, Robert
Publikováno v:
Phys.Rev.D81:084031,2010
We construct an instanton describing the pair production of non-Kaluza Klein bubbles of nothing in higher odd dimensional de Sitter spaces. In addition to showing that higher dimensional de Sitter spaces have a nonzero probability to become topologic
Externí odkaz:
http://arxiv.org/abs/1001.2266
Publikováno v:
JHEP 0912:047,2009
We describe a number of striking features of a class of smooth solitons in gauged and ungauged minimal supergravity in five dimensions. The solitons are globally asymptotically flat or asymptotically AdS without any Kaluza-Klein directions but contai
Externí odkaz:
http://arxiv.org/abs/0909.3289
Autor:
Copsey, Keith, Mann, Robert B.
Publikováno v:
JHEP0805:069,2008
We develop a careful definition of energy for nonsupersymmetric warped product asymptotically $AdS_d \times M_q$ solutions which include a nonzero p-form. In the case of an electric p-form extending along all the AdS directions, and in particular in
Externí odkaz:
http://arxiv.org/abs/0803.3801