9 research outputs found
On Geodesic Motion in Horava-Lifshitz Gravity
We propose an action for a free particle in Horava-Lifshitz gravity based on
Foliation Preserving Diffeomorphisms. The action reduces to the usual
relativistic action in the low energy limit and allows for subluminal and
superluminal motions with upper and lower bounds on velocity respectively. We
find that deviation from general relativity is governed by a position dependent
coupling constant which also depends on the mass of the particle. As a result,
light-like geodesics are not affected whereas massive particles follow
geodesics that become mass dependent and hence the equivalence principle is
violated. We make an exact study for geodesics in flat space and a qualitative
analysis for those in a spherically symmetric curved background.Comment: 12 pages, Dedicated to Farhad Ardalan on his 70th birthda
Temperature in the Throat
We study the temperature of extended objects in string theory. Rotating probe
D-branes admit horizons and temperatures a la Unruh effect. We find that the
induced metrics on slow rotating probe D1-branes in holographic string
solutions including warped Calabi-Yau throats have distinct thermal horizons
with characteristic Hawking temperatures even if there is no black hole in the
bulk Calabi-Yau. Taking the UV/IR limits of the solution, we show that the
world volume black hole nucleation depends on the deformation and the warping
of the throat. We find that world volume horizons and temperatures of expected
features form not in the regular confining IR region but in the singular
nonconfining UV solution. In the conformal limit of the UV, we find horizons
and temperatures similar to those on rotating probes in the AdS throat found in
the literature. In this case, we also find that activating a background gauge
field form the U(1) R--symmetry modifies the induced metric with its
temperature describing two different classes of black hole solutions.Comment: Revised, extended and published versio
Quantum Local Quench, AdS/BCFT and Yo-Yo String
We propose a holographic model for local quench in 1+1 dimensional Conformal
Field Theory (CFT). The local quench is produced by joining two identical CFT's
on semi-infinite lines. When these theories have a zero boundary entropy, we
use the AdS/Boundary CFT proposal to describe this process in terms of bulk
physics. Boundaries of the original CFT's are extended in AdS as dynamical
surfaces. In our holographic picture these surfaces detach from the boundary
and form a closed folded string which can propagate in the bulk. The dynamics
of this string is governed by the tensionless Yo-Yo string solution and its
subsequent evolution determines the time dependence after quench. We use this
model to calculate holographic Entanglement Entropy (EE) of an interval as a
function of time. We propose how the falling string deforms Ryu-Takayanagi's
curves. Using the deformed curves we calculate EE and find complete agreement
with field theory results.Comment: 20 pages, 13 figures, discussion improved, Version to appear in JHE
Dual Spikes; New Spiky String Solutions
We find a new class of spiky solutions for closed strings in flat,
and backgrounds. In the flat
case the new solutions turn out to be T-dual configurations of spiky strings
found by Kruczenski hep-th/0410226. In the case of solutions living in ,
we make a semi classical analysis by taking the large angular momentum limit.
The anomalous dimension for these dual spikes is similar to that for rotating
and pulsating circular strings in AdS with angular momentum playing the role of
the level number. This replaces the well known logarithmic dependence for
spinning strings. For the dual spikes living on sphere we find that no large
angular momentum limit exists.Comment: Added reference
Symmetric Orbifolds and Entanglement Entropy for Primary Excitations in Two Dimensional CFT
We use the techniques in symmetric orbifolding to calculate the Entanglement Entropy of a single interval in a two dimensional conformal field theory on a circle which is excited to a pure highest weight state. This is achieved by calculating the Reney Entropy which is found in terms of a 2n-point function of primary operators, n being the replica number