123 research outputs found
Holographic quantum phase transitions and interacting bulk scalars
We consider a system of two massive, mutually interacting probe real scalar
fields, in zero temperature holographic backgrounds. The system does not have
any continuous symmetry. For a suitable range of the interaction parameters
adhering to the interaction potential between the bulk scalars, we have shown
that as one turns on the source for one scalar field, the system may go through
a second order quantum critical phase transition across which the second scalar
field forms a condensate. We have looked at the resulting phase diagram and
numerically computed the condensate. We have also investigated our system in
two different backgrounds: and soliton, and got similar phase
structure.Comment: 5 pages, 6 figure
Integrability Lost
It is known that classical string dynamics in pure AdS_5\times S^5 is
integrable and plays an important role in solvability. This is a deep and
central issue in holography. Here we investigate similar classical
integrability for a more realistic confining background and provide a negative
answer. The dynamics of a class of simple string configurations in AdS soliton
background can be mapped to the dynamics of a set of non-linearly coupled
oscillators. In a suitable limit of small fluctuations we discuss a
quasi-periodic analytic solution of the system. However numerics indicates
chaotic behavior as the fluctuations are not small. Integrability implies the
existence of a regular foliation of the phase space by invariant manifolds. Our
numerics shows how this nice foliation structure is eventually lost due to
chaotic motion. We also verify a positive Lyapunov index for chaotic orbits.
Our dynamics is roughly similar to other known non-integrable coupled
oscillators systems like Henon-Heiles equations.Comment: Acknowledged grant
Plasma balls/kinks as solitons of large confining gauge theories
We discuss finite regions of the deconfining phase of a confining gauge
theory (plasma balls/kinks) as solitons of the large , long wavelength,
effective Lagrangian of the thermal gauge theory expressed in terms of suitable
order parameters. We consider a class of confining gauge theories whose
effective Lagrangian turns out to be a generic 1 dim. unitary matrix model. The
dynamics of this matrix model can be studied by an exact mapping to a
non-relativistic many fermion problem on a circle. We present an approximate
solution to the equations of motion which corresponds to the motion (in
Euclidean time) of the Fermi surface interpolating between the phase where the
fermions are uniformly distributed on the circle (confinement phase) and the
phase where the fermion distribution has a gap on the circle (deconfinement
phase). We later self-consistently verify that the approximation is a good one.
We discuss some properties and implications of the solution including the
surface tension which turns out to be positive. As a by product of our
investigation we point out the problem of obtaining time dependent solutions in
the collective field theory formalism due to generic shock formation.Comment: 26+1 pages, 10 figure
AdS (In)stability: Lessons From The Scalar Field
We argued in arXiv:1408.0624 that the quartic scalar field in AdS has
features that could be instructive for answering the gravitational stability
question of AdS. Indeed, the conserved charges identified there have recently
been observed in the full gravity theory as well. In this paper, we continue
our investigation of the scalar field in AdS and provide evidence that in the
Two-Time Formalism (TTF), even for initial conditions that are far from
quasi-periodicity, the energy in the higher modes at late times is
exponentially suppressed in the mode number. Based on this and some related
observations, we argue that there is no thermalization in the scalar TTF model
within time-scales that go as , where measures
the initial amplitude (with only low-lying modes excited). It is tempting to
speculate that the result holds also for AdS collapse.Comment: 10 pages, 4 figure
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