1,246 research outputs found
CFT/CFT interpolating RG flows and the holographic c-function
We consider holographic RG flows which interpolate between non-trivial
ultra-violet (UV) and infra-red (IR) conformal fixed points. We study the
``superpotentials'' which characterize different flows and discuss their
expansions near the fixed points. Then we focus on the holographic -function
as defined from the two-point function of the stress-energy tensor. We point
out that the equation for the metric fluctuations in the background flow is
equivalent to a scattering problem and we use this to obtain an expression for
the -function in terms of the associated Jost functions. We propose two
explicit models that realize UV-IR flows. In the first example we consider a
thin wall separating two AdS spaces with different radii, while in the second
one the UV region is replaced with an asymptotically AdS space. We find that
the holographic -function obeys the expected properties. In particular it
reduces to the correct -- nonzero -- central charge in the IR limit.Comment: 20 pages, discussion at the end of sec. 3 and sec. 4.1 change
A Class of Non-Supersymmetric Open String Vacua
We analyze non-supersymmetric four dimensional open string models of type IIB
string theory compactified on with Scherk-Schwarz deformation
acting on an of the torus. We find that there are always two
solutions to the tadpole conditions that are shown to be connected via Wilson
lines in an non-trivial way. These models although non-supersymmetric, are free
of R-R and NS-NS tadpoles.Comment: 9 pages, no figues, Latex file (v2
String Theory on Dp-plane waves
We study the spectrum of solvable string models on plane waves descending
from non-conformal Dp-brane geometries. We mainly focus on S-dual F1/D1-waves
in type IIB and type I/heterotic 10D superstrings. We derive the Kaluza-Klein
spectrum of N=1,2 10D supergravities on D1/F1-waves. We compute helicity
supertraces counting multiplicities and R-charges of string excitations in the
plane wave geometry. The results are compared against the expectations coming
from gauge/supergravity descriptions. In the type I case, the Klein, Annulus
and Moebius one-loop amplitudes are computed for ten-dimensional D1-waves. We
test the consistency of the open string descendant by showing that after
modular transformations to the closed string channel, the three amplitudes
combine themselves to reconstruct a complete square (|B>+|C>)^2. Tadpole
conditions are also discussed.Comment: 22 pages, Minor corrections, References adde
The abelian cosets of the Heisenberg group
In this paper we study the abelian cosets of the H(4) WZW model. They
coincide or are related to several interesting three-dimensional backgrounds
such as the Melvin model, the conical point-particle space-times and the null
orbifold. We perform a detailed CFT analysis of all the models and compute the
coset characters as well as some typical three-point couplings of coset
primaries.Comment: 26 pages; v2: minor typos corrected, also added section 3.3 and 4.3
with a few comments on a third class of geometries that have not been
discussed in v
A Classification of Toroidal Orientifold Models
We develop the general tools for model building with orientifolds, including
SS supersymmetry breaking. In this paper, we work out the general formulae of
the tadpole conditions for a class of non supersymmetric orientifold models of
type IIB string theory compactified on , based on the general properties
of the orientifold group elements. By solving the tadpoles we obtain the
general anomaly free massless spectrum.Comment: 35 pages, 3 eps figures, Latex2
The one-loop vacuum energy and RG flow induced by double-trace operators in AdS/CFT and dS/CFT correspondence
We calculate the difference of one-loop vacuum energies for massive scalar
field in five-dimensional AdS black hole. (The same is done in five-dimensional
deSitter space). In each case this difference is specified by the boundary
conditions corresponding to the double-trace operator (massive term) and it
describes RG flow in the manner discussed by Gubser-Mitra for pure AdS space.
For AdS black hole there occurs instability which is the manifestation of the
Hawking-Page phase transition. For stable phase of AdS black hole as well as
for deSitter bulk, c-function found beyond the leading order approximation
shows the monotonic behaviour consistent with c-theorem.Comment: LaTeX file, 3 eps files, 26 pages. The discussion is clarified,
version to appear in PR
Holographic Correlators in a Flow to a Fixed Point
Using holographic renormalization, we study correlation functions throughout
a renormalization group flow between two-dimensional superconformal field
theories. The ultraviolet theory is an N=(4,4) CFT which can be thought of as a
symmetric product of U(2) super WZW models. It is perturbed by a relevant
operator which preserves one-quarter supersymmetry and drives the theory to an
infrared fixed point. We compute correlators of the stress-energy tensor and of
the relevant operators dual to supergravity scalars. Using the former, we put
together Zamolodchikov's C function, and contrast it with proposals for a
holographic C function. In passing, we address and resolve two puzzles also
found in the case of five-dimensional bulk supergravity.Comment: LaTeX2e, 48 pages, 4 figure
Hadronic observables from SIS to SPS energies - anything strange with strangeness ?
We calculate and (+) rapidity
distributions and compare to experimental data from SIS to SPS energies within
the UrQMD and HSD transport approaches that are both based on string, quark,
diquark () and hadronic degrees of freedom. The
two transport models do not include any explicit phase transition to a
quark-gluon plasma (QGP). It is found that both approaches agree rather well
with each other and with the experimental rapidity distributions for protons,
's, and . Inspite of this apparent agreement both
transport models fail to reproduce the maximum in the excitation function for
the ratio found experimentally between 11 and 40 AGeV. A
comparison to the various experimental data shows that this 'failure' is
dominantly due to an insufficient description of pion rapidity distributions
rather than missing 'strangeness'. The modest differences in the transport
model results -- on the other hand -- can be attributed to different
implementations of string formation and fragmentation, that are not
sufficiently controlled by experimental data for the 'elementary' reactions in
vacuum.Comment: 46 pages, including 15 eps figures, to be published in Phys. Rev.
A Field-theoretical Interpretation of the Holographic Renormalization Group
A quantum-field theoretical interpretation is given to the holographic RG
equation by relating it to a field-theoretical local RG equation which
determines how Weyl invariance is broken in a quantized field theory. Using
this approach we determine the relation between the holographic C theorem and
the C theorem in two-dimensional quantum field theory which relies on the
Zamolodchikov metric. Similarly we discuss how in four dimensions the
holographic C function is related to a conjectured field-theoretical C
function. The scheme dependence of the holographic RG due to the possible
presence of finite local counterterms is discussed in detail, as well as its
implications for the holographic C function. We also discuss issues special to
the situation when mass deformations are present. Furthermore we suggest that
the holographic RG equation may also be obtained from a bulk diffeomorphism
which reduces to a Weyl transformation on the boundary.Comment: 24 pages, LaTeX, no figures; references added, typos corrected,
paragraph added to section
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