135 research outputs found
Thermal DBI action for the D3-brane at weak and strong coupling
We study the effective action for finite-temperature D3-branes with an
electromagnetic field at weak and strong coupling. We call this action the
thermal DBI action. Comparing at low temperature the leading correction
for the thermal DBI action at weak and strong coupling we find that the
factor well-known from the AdS/CFT correspondence extends to the case of
arbitrary electric and magnetic fields on the D3-brane. We investigate the
reason for this by taking the decoupling limit in both the open and the closed
string descriptions thus showing that the AdS/CFT correspondence extends to the
case of arbitrary constant electric and magnetic fields on the D3-brane.Comment: 30 pages, no figure
Finite-size corrections to the rotating string and the winding state
We compute higher order finite size corrections to the energies of the
circular rotating string on AdS_5 x S^5, of its orbifolded generalization on
AdS_5 x S^5/Z_M and of the winding state which is obtained as the limit of the
orbifolded circular string solution when J -> infinity and J/M^2 is kept fixed.
We solve, at the first order in lambda'=lambda/J^2, where lambda is the 't
Hooft coupling, the Bethe equations that describe the anomalous dimensions of
the corresponding gauge dual operators in an expansion in m/K, where m is the
winding number and K is the "magnon number", and to all orders in the angular
momentum J. The solution for the circular rotating string and for the winding
state can be matched to the energy computed from an effective quantum
Landau-Lifshitz model beyond the first order correction in 1/J. For the leading
1/J corrections to the circular rotating string in m^2 and m^4 and for the
subleading 1/J^2 corrections to the m^2 term, we find agreement. For the
winding state we match the energy completely up to, and including, the order
1/J^2 finite-size corrections. The solution of the Bethe equations
corresponding to the spinning closed string is also provided in an expansion in
m/K and to all orders in J.Comment: v2: 33 pages, misprints corrected, references added, version accepted
for publication in JHE
Exciton Condensation in a Holographic Double Monolayer Semimetal
The formation of intra-layer and inter-layer exciton condensates in a model
of a double monolayer Weyl semi-metal is studied in the strong coupling limit
using AdS/CFT duality. We find a rich phase diagram which includes phase
transitions between inter-layer and intra-layer condensates as the charge
densities and the separation of the layers are varied. The tendency to
inter-layer condensation is strongest when the charge densities are balanced so
that the weak coupling electron and hole Fermi surfaces would be nested. For
systems with multiple species of massless Fermions, we find a novel phase
transition where the charge balance for nesting occurs spontaneously.Comment: 4 pages, 2 figure
Conformal Symmetry and Differential Regularization of the Three-Gluon Vertex
The conformal symmetry of the QCD Lagrangian for massless quarks is broken
both by renormalization effects and the gauge fixing procedure. Renormalized
primitive divergent amplitudes have the property that their form away from the
overall coincident point singularity is fully determined by the bare
Lagrangian, and scale dependence is restricted to -functions at the
singularity. If gauge fixing could be ignored, one would expect these
amplitudes to be conformal invariant for non-coincident points. We find that
the one-loop three-gluon vertex function is
conformal invariant in this sense, if calculated in the background field
formalism using the Feynman gauge for internal gluons. It is not yet clear why
the expected breaking due to gauge fixing is absent. The conformal property
implies that the gluon, ghost and quark loop contributions to
are each purely numerical combinations of two universal
conformal tensors and whose
explicit form is given in the text. Only has an ultraviolet
divergence, although requires a careful definition to resolve
the expected ambiguity of a formally linearly divergent quantity.
Regularization is straightforward and leads to a renormalized vertex function
which satisfies the required Ward identity, and from which the beta-function is
easily obtained. Exact conformal invariance is broken in higher-loop orders,
but we outline a speculative scenario in which the perturbative structure of
the vertex function is determined from a conformal invariant primitive core by
interplay of the renormalization group equation and Ward identities.Comment: 65 page
The Flowing BIon
In this paper we use the effective blackfold description of branes to extend
the study of the thermal BIon, a D-brane and parallel anti-D-brane connected by
a wormhole with F-string charge in hot flat space, by introducing a radial
boost along the brane. The boosted system behaves qualitatively differently
from both the extremal and the thermal BIon considered previously.
Interestingly, we are able to formulate a first law of thermodynamics for the
system as a whole, despite the fact that it is not a stationary blackfold. In
particular, the global temperature is given by the rest frame temperature times
the gamma factor of special relativity which is the inverse transformation
compared to the case of stationary blackfolds. In addition we define two new
kinds of thermodynamic conjugate variables, the energy flux and the
integrated velocity on the brane. We find that a phase transition occurs by
varying the energy flux . Below a critical value of the brane separation
changes only slightly with . Instead above the critical value
grows exponentially.Comment: 26 pages, 6 figures. v2: Introduction and conclusion improved,
references adde
AdS/CFT v.s. String Loops
The one string-loop correction to the energies of two impurity BMN states are
computed using IIB light-cone string field theory with an improved 3-string
vertex that has been proposed by Dobashi and Yoneya. As in previous published
computations, the string vertices are truncated to the 2-impurity channel. The
result is compared with the prediction from non-planar corrections in the BMN
limit of supersymmetric Yang-Mills theory. It is found to agree
at leading order -- one-loop in Yang-Mills theory -- and is close but not quite
in agreement at order two Yang-Mills loops. Furthermore, in addition to the
leading 1/2 power in the t'Hooft coupling, which is generic in string field
theory, and which we have previously argued cancels, we find that the 3/2 and
5/2 powers are also miraculously absent.Comment: 13 page
On the existence of the Blandford-Znajek monopole for a slowly rotating Kerr black hole
The Blandford-Znajek monopole is a conjectured solution of force-free
electrodynamics in the vicinity of a slowly rotating Kerr black hole,
supposedly defined as a perturbation in small angular momentum. It is used to
argue for the extraction of energy from rotating black holes by the
Blandford-Znajek process. We set up a careful analysis of the perturbative
definition of the Blandford-Znajek monopole, showing in particular that the
regime in which it is defined allows to use the technique of matched asymptotic
expansions. Our conclusion is that the Blandford-Znajek monopole, as it is
defined, is not consistent with demanding physically reasonable boundary
conditions far away from the event horizon. This puts into question the
existence of the Blandford-Znajek monopole, at least in the limit of slow
rotation of the Kerr black hole.Comment: 8 pages, pdflatex. v2: minor typos corrected, conclusion improved,
acknowledgments added. v3: published version, references added, MAE
explanation and conclusions slightly expande
- …