6,849 research outputs found
Conductivities for Hyperscaling Violating Geometries
We show that many results about holographic conductivities in geometries with
hyperscaling violating scaling can be reproduced from simple scaling laws in
the dual field theory. We show that the electro-magnetic response of probe
branes in these systems require at least one additional scaling parameter Phi
beyond the usual dynamical exponent z and hyperscaling violating exponent
theta, as also pointed out in earlier work. We show that the scaling exponents
can be chosen in such a way that the temperature dependence of DC conductivity
and Hall angle in strange metals can be reproduced.Comment: 16 pages; v2: references added; v3: comparison to
Einstein-Maxwell-Dilaton system added; version to appear in JHE
Multiband models for field theories with anomalous current dimension
We give simple examples of weakly coupled or free quantum mechanical systems
that exhibit scale invariance with an anomalous dimension for a conserved
current. In these models scaling as an exact symmetry only emerges in a large N
limit, but it remains as an approximate symmetry even at finite N.Comment: 12 pages, 1 figure; v2: references added; v3: missing factor of z
added in (5.4) and (5.5
Adding D7-branes to the Polchinski-Strassler gravity background
We motivate and summarize our analysis of hep-th/0610276 in which we consider
D7-brane probe embeddings in the Polchinski-Strassler background with N=2
supersymmetry. The corresponding dual gauge theory is given by the N=2* theory
with fundamental matter.Comment: Based on a talk given by C.S. at the RTN Workshop and Midterm meeting
2006 in Napoli, LaTeX, 7 pages, 1 table, 1 figur
Boundary Holographic Witten Diagrams
In this paper we discuss geodesic Witten diagrams in generic holographic
conformal field theories with boundary or defect. Boundary CFTs allow two
different decompositions of two-point functions into conformal blocks: boundary
channel and ambient channel. Building on earlier work, we derive a holographic
dual of the boundary channel decomposition in terms of bulk-to-bulk propagators
on lower dimensional AdS slices. In the situation in which we can treat the
boundary or defect as a perturbation around pure AdS spacetime, we obtain the
leading corrections to the two-point function both in boundary and ambient
channel in terms of geodesic Witten diagrams which exactly reproduce the
decomposition into corresponding conformal blocks on the field theory side.Comment: 28 pages, 4 figures, v2:included hypergeometric identities for
generic no-brane case, references added, v3:published versio
Mesons and Higgs branch in defect theories
We consider the defect theory obtained by intersecting D3- and D5-branes
along two common spatial directions. We work in the approximation in which the
D5-brane is a probe in the AdS_5xS^5 background. By adding worldvolume flux to
the D5-brane and choosing an appropriate embedding of the probe in AdS_5xS^5,
one gets a supersymmetric configuration in which some of the D3-branes
recombine with the D5-brane. We check this fact by showing that the D5-brane
can be regarded as a system of polarized D3-branes. On the field theory side
this corresponds to the Higgs branch of the defect theory, where some of the
fundamental hypermultiplet fields living on the intersection acquire a vacuum
expectation value. We study the spectrum of mesonic bound states of the defect
theory in this Higgs branch and show that it is continuous and gapless.Comment: 15 pages, LaTe
Hadron Masses and Screening from AdS Wilson Loops
We show that in strongly coupled N=4 SYM the binding energy of a heavy and a
light quark is independent of the strength of the coupling constant. As a
consequence we are able to show that in the presence of light quarks the analog
of the QCD string can snap and color charges are screened. The resulting
neutral mesons interact with each other only via pion exchange and we estimate
the massesComment: 4 pages, revte
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