13 research outputs found
Quantum Corrections to Lorentz Invariance Violating Theories: Fine-Tuning Problem
It is of general agreement that a quantum gravity theory will most probably
mean a breakdown of the standard structure of space-time at the Planck scale.
This has motivated the study of Planck-scale Lorentz Invariance Violating (LIV)
theories and the search for its observational signals. Yet, it has been
recently shown that, in a simple scalar-spinor Yukawa theory, radiative
corrections to tree-level Planck-scale LIV theories can induce large Lorentz
violations at low energies, in strong contradiction with experiment, unless an
unnatural fine-tuning mechanism is present. In this letter, we show the
calculation of the electron self-energy in the framework given by the
Myers-Pospelov model for a Lorentz Invariance Violating QED. We find a
contribution that depends on the prefered's frame four-velocity which is not
Planck-scale suppressed, showing that this model suffers from the same disease.
Comparison with Hughes-Drever experiments requires a fine-tuning of 21 orders
of magnitude for this model not to disagree with experiment.Comment: 10 pages, no figures. Version acceptd in Physics Letters
Moduli space of supersymmetric solitons and black holes in five dimensions
We determine all asymptotically flat, supersymmetric and biaxisymmetric
soliton and black hole solutions to five dimensional minimal supergravity. In
particular, we show that the solution must be a multi-centred solution with a
Gibbons-Hawking base. The proof involves combining local constraints from
supersymmetry with global constraints for stationary and biaxisymmetric
spacetimes. This reveals that the horizon topology must be one of S^3, S^1 x
S^2 or a lens space L(p,1), thereby providing a refinement of the allowed
horizon topologies. We construct the general smooth solution for each possible
rod structure. We find a large moduli space of black hole spacetimes with
noncontractible 2-cycles for each of the allowed horizon topologies. In the
absence of a black hole we obtain a classification of the known `bubbling'
soliton spacetimes.Comment: v2: 43 pages, 5 figures, references added, typos fixed, minor
clarifications, expanded discussion of physical parameters. v3: clarified
statement of theorem 4 (results unchanged, update made after publication
The 5d superconformal index at large N and black holes
We study the large N limit of the superconformal index of a large class of 5d N = 1 superconformal field theories and show it is given by the square of the partition function on the squashed five-sphere. We show this simple relation implies a Cardy formula in 5d, which is valid in an âextendedâ regime in which fugacities are finite and N is large. For theories with weakly coupled gravity duals we conjecture this large N Cardy formula universally accounts for the microscopic entropy of spinning black holes in AdS6. We check this explicitly for known black hole solutions in massive type IIA and type IIB string theory, carrying two angular momenta and one electric charge, and predict the entropy of black holes carrying multiple electric charges, yet to be constructed. We also discuss large N properties of the Sb3Â Ă ÎŁg partition function, extending previous results to theories with type IIB duals