58 research outputs found
Correlation functions in a cascading N=1 gauge theory from supergravity
We study fluctuations around the warped conifold supergravity solution of
Klebanov and Tseytlin [hep-th/0002159], known to be dual to a cascading N=1
gauge theory. Although this supergravity background is not asymptotically AdS,
corresponding to a non-conformal field theory, it is possible to apply the
usual methods of AdS/CFT duality to extract the high energy behavior of field
theory correlators by solving linearized equations of motion for fluctuations
around the background. We consider the Goldstone vector dual to the anomalous
R-symmetry current and compute its mass, which exactly matches the general
prediction of [hep-th/0009156]. We find the high energy 2-point functions for
the R-current and two other vectors. As expected, the R-current 2-point
function has a longitudinal part because R-symmetry is broken. We also
calculate the high energy 2-point function of the energy-momentum tensor from
fluctuations of modes in the graviton sector. This 2-point function has a trace
part corresponding to broken conformal symmetry.Comment: JHEP, 29 page
Scalar Absorption and the Breaking of the World Volume Conformal Invariance
We investigate a version of fixed scalars for non-dilatonic branes which
correspond to dilatations of the brane world-volume. We obtain a cross-section
whose world-volume interpretation falls out naturally from an investigation of
the breaking of conformal invariance by the irrelevant Born-Infeld corrections
to Yang-Mills theory. From the same irrelevant world-volume operator we obtain
the leading correction to the cross-sections of minimal scalars. This
correction can be obtained in supergravity via an improved matching of inner
and outer solutions to the minimal wave equation.Comment: 20 pages, 2 figures. Minor change
Towards Holographic Renormalization of Fake Supergravity
A step is made towards generalizing the method of holographic renormalization
to backgrounds which are not asymptotically AdS, corresponding to a dual gauge
theory which has logarithmically running couplings even in the ultraviolet. A
prime example is the background of Klebanov-Strassler (KS). In particular, a
recipe is given how to calculate renormalized two-point functions for the
operators dual to the bulk scalars. The recipe makes use of gauge-invariant
variables for the fluctuations around the background and works for any bulk
theory of the fake supergravity type. It elegantly incorporates the
renormalization scheme dependence of local terms in the correlators. Before
applying the method to the KS theory, it is verified that known results in
asymptotically AdS backgrounds are reproduced. Finally, some comments on the
calculation of renormalized vacuum expectation values are made.Comment: 33 pages, v2: reference added, small change
Closed String Tachyons and Their Implications for Non-Supersymmetric Strings
Closed string tachyons have long been somewhat mysterious. We note that there
is often a regime in the classical moduli space in which one can systematically
compute the effective action for such fields. In this regime, the tachyon is
light, and cannot be integrated out. Instead, one must consider the combined
dynamics of gravitons, moduli, tachyons and other light fields. We compute the
action and find that the quartic term for the tachyon is positive in the field
definition where the tachyon has no derivative coupling to the radion. We study
the evolution of isotropic, homogeneous configurations and find that typically
the system is driven to regions where the calculation is no longer under
control.Comment: 10 pages, no figures, references adde
QCD thermodynamics with two flavors of Wilson quarks at N_t=6
We report on a study of hadron thermodynamics with two flavors of Wilson
quarks on 12^3x6 lattices. We have studied the crossover between the high and
low temperature regimes for three values of the hopping parameter, kappa=0.16,
0.17, and 0.18. At each of these values of kappa we have carried out spectrum
calculations on 12^3x24 lattices for two values of the gauge coupling in the
vicinity of the crossover in order to set an energy scale for our
thermodynamics calculations and to determine the critical value of the gauge
coupling for which the pion and quark masses vanish. For kappa=0.17 and 0.18 we
find coexistence between the high and low temperature regimes over 1,000
simulation time units indicating either that the equilibration time is
extremely long or that there is a possibility of a first order phase
transition. The pion mass is large at the crossover values of the gauge
coupling, but the crossover curve has moved closer to the critical curve along
which the pion and quark masses vanish, than it was on lattices with four time
slices. In addition, values of the dimensionless quantity T_c/m_rho are in
closer agreement with those for staggered quarks than was the case at N_t=4. (A
POSTSCRIPT VERSION OF THIS PAPER IS AVAILABLE BY ANONYMOUS FTP FROM
sarek.physics.ucsb.edu (128.111.8.250) IN THE FILE pub/wilson_thermo.ps)Comment: 24 page
Bulk Dynamics in Confining Gauge Theories
We consider gauge/string duality (in the supergravity approximation) for
confining gauge theories. The system under scrutiny is a 5-dimensional
consistent truncation of type IIB supergravity obtained using the
Papadopoulos-Tseytlin ansatz with boundary momentum added. We develop a
gauge-invariant and sigma-model-covariant approach to the dynamics of
5-dimensional bulk fluctuations. For the Maldacena-Nunez subsystem, we study
glueball mass spectra. For the Klebanov-Strassler subsystem, we compute the
linearized equations of motion for the 7-scalar system, and show that a
3-scalar sector containing the scalar dual to the gluino bilinear decouples in
the UV. We solve the fluctuation equations exactly in the "moderate UV"
approximation and check this approximation numerically. Our results demonstrate
the feasibility of analyzing the generally coupled equations for scalar bulk
fluctuations, and constitute a step on the way towards computing correlators in
confining gauge theories.Comment: 60 pages, 4 figures, v2: corrected typos, added references, v3: added
reference
Hadron Spectrum in QCD with Valence Wilson Fermions and Dynamical Staggered Fermions at $6/g^2=5.6
We present an analysis of hadronic spectroscopy for Wilson valence quarks
with dynamical staggered fermions at lattice coupling at
sea quark mass and 0.025, and of Wilson valence quarks in quenched
approximation at and 5.95, both on lattices. We
make comparisons with our previous results with dynamical staggered fermions at
the same parameter values but on lattices doubled in the temporal
direction.Comment: 32 page
Effects of spatial size, lattice doubling and source operator on the hadron spectrum with dynamical staggered quarks
We have extended our previous study of the lattice QCD spectrum with 2
flavors of staggered dynamical quarks at and and 0.01
to larger lattices, with better statistics and with additional sources for the
propagators. The additional sources allowed us to estimate the mass
and to measure the masses of all mesons whose operators are local in time.
These mesons show good evidence for flavor symmetry restoration, except for the
masses of the Goldstone and non-Goldstone pions. PCAC is observed in that
, and is estimated. Use of undoubled lattices
removes problems with the pion propagator found in our earlier work. Previously
we found a large change in the nucleon mass at a quark mass of when
we increased the spatial size from 12 to 16. No such effect is observed at the
larger quark mass, . Two kinds of wall source were used, and we
have found difficulties in getting consistent results for the nucleon mass
between the two sources.Comment: 30 pages PostScript fil
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