500 research outputs found
Gravitational collapse and thermalization in the hard wall model
We study a simple example of holographic thermalization in a confining field
theory: the homogeneous injection of energy in the hard wall model. Working in
an amplitude expansion, we find black brane formation for sufficiently fast
energy injection and a scattering wave solution for sufficiently slow
injection. We comment on our expectations for more sophisticated holographic
QCD models.Comment: 33 pages, 5 figure
The holographic quantum effective potential at finite temperature and density
We develop a formalism that allows the computation of the quantum effective
potential of a scalar order parameter in a class of holographic theories at
finite temperature and charge density. The effective potential is a valuable
tool for studying the ground state of the theory, symmetry breaking patterns
and phase transitions. We derive general formulae for the effective potential
and apply them to determine the phase transition temperature and density in the
scaling region.Comment: 27 page
Predictions for PP-wave string amplitudes from perturbative SYM
The role of general two-impurity multi-trace operators in the BMN
correspondence is explored. Surprisingly, the anomalous dimensions of all
two-impurity multi-trace BMN operators to order g_2^2\lambda' are completely
determined in terms of single-trace anomalous dimensions. This is due to
suppression of connected field theory diagrams in the BMN limit and this fact
has important implications for some string theory processes on the PP-wave
background. We also make gauge theory predictions for the matrix elements of
the light-cone string field theory Hamiltonian in the two string-two string and
one string-three string sectors.Comment: 46 pages, 12 figures. V3:typos correcte
Holography and Thermodynamics of 5D Dilaton-gravity
The asymptotically-logarithmically-AdS black-hole solutions of 5D dilaton
gravity with a monotonic dilaton potential are analyzed in detail. Such
theories are holographically very close to pure Yang-Mills theory in four
dimensions. The existence and uniqueness of black-hole solutions is shown. It
is also shown that a Hawking-Page transition exists at finite temperature if
and only if the potential corresponds to a confining theory. The physics of the
transition matches in detail with that of deconfinement of the Yang-Mills
theory. The high-temperature phase asymptotes to a free gluon gas at high
temperature matching the expected behavior from asymptotic freedom. The thermal
gluon condensate is calculated and shown to be crucial for the existence of a
non-trivial deconfining transition. The condensate of the topological charge is
shown to vanish in the deconfined phase.Comment: LaTeX, 61 pages (main body) + 58 pages (appendix), 25 eps figures.
Revised version, published in JHEP. Two equations added in Section 7.4; typos
corrected; references adde
Holographic Conformal Window - A Bottom Up Approach
We propose a five-dimensional framework for modeling the background geometry
associated to ordinary Yang-Mills (YM) as well as to nonsupersymmetric gauge
theories possessing an infrared fixed point with fermions in various
representations of the underlying gauge group. The model is based on the
improved holographic approach, on the string theory side, and on the
conjectured all-orders beta function for the gauge theory one. We first analyze
the YM gauge theory. We then investigate the effects of adding flavors and show
that, in the holographic description of the conformal window, the geometry
becomes AdS when approaching the ultraviolet and the infrared regimes. As the
number of flavors increases within the conformal window we observe that the
geometry becomes more and more of AdS type over the entire energy range.Comment: 20 Pages, 3 Figures. v2: references adde
Instability and Degeneracy in the BMN Correspondence
Non-degenerate perturbation theory, which was used to calculate the scale
dimension of operators on the gauge theory side of the correspondence, breaks
down when effects of triple trace operators are included. We interpret this as
an instability of excited single-string states in the dual string theory for
decay into the continuum of degenerate 3-string states. We apply time-dependent
perturbation theory to calculate the decay widths from gauge theory. These
widths are new gauge theory data which can be compared with future calculations
in light cone string field theory.Comment: 23 pages, no figure
Heavy quarks in a magnetic field
The motion of a heavy charged quark in a magnetic field is analyzed in the
vacuum of strongly coupled CFT. The motion of the quark is dissipative. It
moves in spiral until it eventually comes to rest. The world-sheet geometry is
locally AdS_2 but has a time dependent horizon. The string profile in the
static gauge extends from the boundary till a point where an embedding
singularity exists. Connections with other circular string motions are
established.Comment: (v3) Misprints corrected, discussion on moving horizons improved and
enhance
Black-hole quasinormal modes and scalar glueballs in a finite-temperature AdS/QCD model
We use the holographic AdS/QCD soft-wall model to investigate the spectrum of
scalar glueballs in a finite temperature plasma. In this model, glueballs are
described by a massless scalar field in an AdS_5 black hole with a dilaton
soft-wall background. Using AdS/CFT prescriptions, we compute the boundary
retarded Green's function. The corresponding thermal spectral function shows
quasiparticle peaks at low temperatures. We also compute the quasinormal modes
of the scalar field in the soft-wall black hole geometry. The temperature and
momentum dependences of these modes are analyzed. The positions and widths of
the peaks of the spectral function are related to the frequencies of the
quasinormal modes. Our numerical results are found employing the power series
method and the computation of Breit-Wigner resonances.Comment: Revision: Results unchanged. More discussions on the model and on the
results. References added. 28 pages, 7 figures, 5 table
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