268 research outputs found
Supersymmetric Backgrounds and Black Holes in Cosmological New Massive Supergravity
Using an off-shell Killing spinor analysis we perform a systematic
investigation of the supersymmetric background and black hole solutions of the
Cosmological New Massive Gravity model. The solutions with a
null Killing vector are the same pp-wave solutions that one finds in the model but we find new solutions with a time-like Killing vector that are
absent in the case. An example of such a solution is a Lifshitz
spacetime. We also consider the supersymmetry properties of the so-called
rotating hairy BTZ black holes and logarithmic black holes in an
background. Furthermore, we show that under certain assumptions there is no
supersymmetric Lifshitz black hole solution.Comment: 27 pages, v2: Typos Corrected, Version appeared in JHE
No Scalar-Haired Cauchy Horizon Theorem in Charged Gauss-Bonnet Black Holes
Recently, a ``no inner (Cauchy) horizon theorem" for static black holes with
non-trivial scalar hairs has been proved in Einstein-Maxwell-scalar theories
and also in Einstein-Maxwell-Horndeski theories with the non-minimal coupling
of a charged (complex) scalar field to Einstein tensor. In this paper, we study
an extension of the theorem to the static black holes in
Einstein-Maxwell-Gauss-Bonnet-scalar theories, or simply, charged Gauss-Bonnet
(GB) black holes. We find that no inner horizon with charged scalar hairs is
allowed for the planar (k=0) black holes, as in the case without GB term. On
the other hand, for the non-planar (k=+1,-1) black holes, we find that the
haired inner horizon can not be excluded due to GB effect generally, though we
can not find a simple condition for its existence. As some explicit examples of
the theorem, we study numerical GB black hole solutions with charged scalar
hairs and Cauchy horizons in asymptotically anti-de Sitter space, and find good
agreements with the theorem. As a byproduct, we find a ``no-go theorem" for
charged de Sitter GB black holes with charged scalar hairs in arbitrary
dimensions.Comment: 21 pages, 8 figure
Symmetries and Conservation Laws in Horava Gravity
Horava gravity has been proposed as a renormalizable quantum gravity without
the ghost problem through anisotropic scaling dimensions which break Lorentz
symmetry in UV. In the Hamiltonian formalism, due to the Lorentz-violating
terms, the constraint structure looks quite different from that of general
relativity (GR) but we have recently found that "there exists the case where we
can recover the same number of degrees of freedom as in GR", in a rather
general set-up. In this paper, we study its Lagrangian perspectives and examine
the full diffeomorphism (Diff) symmetry and its associated conservation laws in
Horava gravity. Surprisingly, we find that the full Diff symmetry in the action
can also be recovered when a certain condition, called "super-condition", which
super-selects the Lorentz-symmetric sector in Horava gravity, is satisfied.
This indicates that the broken Lorentz symmetry, known as
"foliation-preserving" Diff, is just an "apparent" symmetry of the Horava
gravity action and rather its "full action symmetry can be as large as the Diff
in GR ". The super-condition exactly corresponds to the tertiary constraint in
Hamiltonian formalism which is the second-class constraint and provides a
non-trivial realization of the Lorentz symmetry otherwise being absent
apparently. From the recovered Lorentz symmetry in the action, we obtain the
conservation laws with the Noether currents as in covariant theories. The
general formula for the conserved Noether charges reproduces the mass of
four-dimensional static black holes with an "arbitrary" cosmological constant
in Horava gravity, and is independent of ambiguities associated with the choice
of asymptotic boundaries. We also discuss several challenging problems,
including its implications to Hamiltonian formalism, black hole thermodynamics,
radiations from colliding black holes.Comment: 18 pages, no figure
The Hamiltonian Dynamics of Horava Gravity
We consider the Hamiltonian formulation of Horava gravity in arbitrary
dimensions, which has been proposed as a renormalizable gravity model for
quantum gravity without the ghost problem. We study the "full" constraint
analysis of the "non-projectable" Horava gravity whose potential, V(R), is an
arbitrary function of the (intrinsic) Ricci scalar R. We find that there exist
generally distinct cases of this theory, depending on (i) whether the
Hamiltonian constraint generates new (second-class) constraints (Cases A, C) or
just fixes the associated Lagrange multipliers (Case B), or (ii) whether the IR
Lorentz-deformation parameter \lambda is at the conformal point (Case C) or not
(Cases A, B). It is found that, for Cases A and C, the dynamical degrees of
freedom are the same as in general relativity, while, for Case B, there is "one
additional phase-space degree of freedom", representing an extra (odd) scalar
graviton mode. This would resolve the long-standing debates about the extra
graviton modes and achieves the dynamical consistency of the Horava gravity, at
the "fully non-linear" level. Several exact solutions are also considered as
some explicit examples of the new constraints. The structure of the newly
obtained, "extended" constraint algebra seems to be generic to Horava gravity
and its general proof would be a challenging problem. Some other challenging
problems, which include the path integral quantization and the Dirac bracket
quantization are discussed also.Comment: Matches published version, Typos correcte
Effect of sourdough addition and storage time on in vitro starch digestibility and estimated glycemic index of tef bread
The effect of sourdough amount and storage time on starch digestibility and estimated glycemic index (eGI) of tef bread was investigated. The rapidly digestible starch (RDS), slowly digestible starch (SDS) and resistant starch (RS) of 0-30% sourdough fresh tef breads ranged from 49 to 58, 16 to 29 and 20 to 26 g/100 g starch, respectively. Storage of tef breads up to 5 days decreased the RDS by more than 2-fold while SDS and RS increased by 2 and 3 fold, respectively. The eGI for fresh and stored breads ranged from 39 to 89. Addition of sourdough increased the eGI of fresh breads while no uniform pattern was seen in the stored breads. As the storage time increased, all the breads showed a decrease in eGI. In vivo study is necessary to further investigate the effect of sourdough on GI of tef bread
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