51 research outputs found
Black hole elasticity and gapped transverse phonons in holography
We study the elastic response of planar black hole (BH) solutions in a simple
class of holographic models with broken translational invariance. We compute
the transverse quasi-normal mode spectrum and the propagation speed of the
lowest energy mode. We find that the speed of the lowest mode relates to the BH
rigidity modulus as dictated by elasticity theory. This allows to identify
these modes as transverse phonons---the pseudo Goldstone bosons of
spontaneously broken translational invariance. In addition, we show that these
modes have a mass gap controlled by an explicit source of the translational
symmetry breaking. These results provide a new confirmation that the BHs in
these models do exhibit solid properties that become more manifest at low
temperatures. Also, by the AdS/CFT correspondence, this allows to extend the
standard results from the effective field theory for solids to quantum-critical
materials.Comment: 28 pages, 7 figures; v3: minor revisions, matching JHEP published
versio
Micro Black Holes and the Democratic Transition
Unitarity implies that the evaporation of microscopic quasi-classical black
holes cannot be universal in different particle species. This creates a puzzle,
since it conflicts with the thermal nature of quasi-classical black holes,
according to which all the species should see the same horizon and be produced
with the same Hawking temperatures. We resolve this puzzle by showing that for
the microscopic black holes, on top the usual quantum evaporation time, there
is a new time-scale which characterizes a purely classical process during which
the black hole looses the ability to differentiate among the species, and
becomes democratic. We demonstrate this phenomenon in a well-understood
framework of large extra dimensions, with a number of parallel branes. An
initially non-democratic black hole is the one localized on one of the branes,
with its high-dimensional Schwarzschild radius being much shorter than the
interbrane distance. Such a black hole seemingly cannot evaporate into the
species localized on the other branes, that are beyond its reach. We
demonstrate that in reality the system evolves classically in time, in such a
way that the black hole accretes the neighboring branes. The end result is a
completely democratic static configuration, in which all the branes share the
same black hole, and all the species are produced with the same Hawking
temperature. Thus, just like their macroscopic counterparts, the microscopic
black holes are universal bridges to the hidden sector physics.Comment: 35 pages, 5 figure
Escape from supercooling with or without bubbles: gravitational wave signatures
Quasi-conformal models are an appealing scenario that can offer naturally a
strongly supercooled phase transition and a period of thermal inflation in the
early Universe. A crucial aspect for the viability of these models is how the
Universe escapes from the supercooled state. One possibility is that thermal
inflation phase ends by nucleation and percolation of true vacuum bubbles. This
route is not, however, always efficient. In such case another escape mechanism,
based on the growth of quantum fluctuations of the scalar field that eventually
destabilize the false vacuum, becomes relevant. We study both of these cases in
detail in a simple yet representative model. We determine the duration of the
thermal inflation, the curvature power spectrum generated for the scales that
exit horizon during the thermal inflation, and the stochastic gravitational
wave background from the phase transition. We show that these gravitational
waves provide an observable signal from the thermal inflation in almost the
entire parameter space of interest. Furthermore, the shape of the gravitational
wave spectrum can be used to ascertain how the Universe escaped from
supercooling.Comment: 11 pages, 6 figures. published versio
Critical escape velocity of black holes from branes
In recent work we have shown that a black hole stacked on a brane escapes
once it acquires a recoil velocity. This result was obtained in the {\it
probe-brane} approximation, {\it i.e.}, when the tension of the brane is
negligibly small. Therefore, it is not clear whether the effect of the brane
tension may prevent the black hole from escaping for small recoil velocities.
The question is whether a critical escape velocity exists. Here, we analyze
this problem by studying the interaction between a Dirac-Nambu-Goto brane and a
black hole assuming adiabatic (quasi-static) evolution. By describing the brane
in a fixed black hole spacetime, which restricts our conclusions to lowest
order effects in the tension, we find that the critical escape velocity does
not exist for co-dimension one branes, while it does for higher co-dimension
branes.Comment: 10 pages, revte
Flux Periodicities and Quantum Hair on Holographic Superconductors
Superconductors in a cylindrical geometry respond periodically to a
cylinder-threading magnetic flux, with the period changing from hc/2e to hc/e
depending on whether the Aharonov-Bohm effects are suppressed or not. We show
that Holographic Superconductors present a similar phenomenon, and that the
different periodicities follow from classical no-hair theorems. We also give
the Ginzburg-Landau description of the period-doubling phenomenon.Comment: 4 pages, 3 figures; article published in Physical Review Letter
Cascading DGP
We present a higher codimension generalization of the DGP scenario which,
unlike previous attempts, is free of ghost instabilities. The 4D propagator is
made regular by embedding our visible 3-brane within a 4-brane, each with their
own induced gravity terms, in a flat 6D bulk. The model is ghost-free if the
tension on the 3-brane is larger than a certain critical value, while the
induced metric remains flat. The gravitational force law `cascades' from a 6D
behavior at the largest distances followed by a 5D and finally a 4D regime at
the shortest scales.Comment: 4 pages; one reference added and a typo correcte
Dynamics of domain walls intersecting black holes
Previous studies concerning the interaction of branes and black holes
suggested that a small black hole intersecting a brane may escape via a
mechanism of reconnection. Here we consider this problem by studying the
interaction of a small black hole and a domain wall composed of a scalar field
and simulate the evolution of this system when the black hole acquires an
initial recoil velocity. We test and confirm previous results, however, unlike
the cases previously studied, in the more general set-up considered here, we
are able to follow the evolution of the system also during the separation, and
completely illustrate how the escape of the black hole takes place.Comment: 4 pages, 6 figure
Vacuum destabilization from Kaluza-Klein modes in an inflating brane
We discuss the effects from the Kaluza-Klein modes in the brane world
scenario when an interaction between bulk and brane fields is included. We
focus on the bulk inflaton model, where a bulk field drives inflation in
an almost bulk bounded by an inflating brane. We couple to a
brane scalar field representing matter on the brane. The bulk field
is assumed to have a light mode, whose mass depends on the expectation
value of . To estimate the effects from the KK modes, we compute the
1-loop effective potential V_\eff(\phi). With no tuning of the parameters of
the model, the vacuum becomes (meta)stable -- V_\eff(\phi) develops a true
vacuum at a nonzero . In the true vacuum, the light mode of
becomes heavy, degenerates with the KK modes and decays. We comment on some
implications for the bulk inflaton model. Also, we clarify some aspects of the
renormalization procedure in the thin wall approximation, and show that the
fluctuations in the bulk and on the brane are closely related.Comment: 15 pages, 2 eps figures. Notation improved, references adde
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