3,069 research outputs found
Match Probability Statistics and Gamma Ray Burst Recurrences in the BATSE Catalog
We develop match probability statistics to test the recurrences of gamma ray
bursts in the BATSE catalog 1B and 2B. We do not find a signal of repetitions
at the match level of 1.e-3.Comment: 4 pages, LaTeX, two macros included (kluwer.sty, spacekap.sty) To
appear in the proceedings of the Eslab29 symposium, ``gamma ray bursts:
toward the source
Holographic Construction of Technicolor Theory
We construct a dual description of technicolor theory based on the D4/D8
brane configuration. A strongly-coupled technicolor theory is identified as the
effective theory on D-branes, and from the gauge/gravity correspondence, we
explore the weakly-coupled holographic description of dynamical electroweak
symmetry breaking. It is found from the D-brane probe action that the masses of
W and Z bosons are given by the decay constant of technipion, and the
technimesons become hierarchically heavy. Moreover, the couplings of heavier
modes to standard model fermions are rather suppressed. The oblique correction
parameters are also evaluated and found to be small except for the S parameter,
which can be reduced by modifying the model. The fermion fields are introduced
at the intersections of D-branes and their masses are generated via massive
gauge bosons from open strings stretching between D-branes.Comment: 23 pages; references added, minor change
Adjoint Trapping: A New Phenomenon at Strong 't Hooft Coupling
Adding matter of mass m, in the fundamental representation of SU(N), to N=4
supersymmetric Yang-Mills theory, we study ``generalized quarkonium''
containing a (s)quark, an anti(s)quark, and J massless (or very light) adjoint
particles. At large 't Hooft coupling >> 1, the states of spin <= 1
are surprisingly light (Kruczenski et al., hep-th/0304032) and small
(hep-th/0312071) with a J-independent size of order . This
``trapping'' of adjoint matter in a region small compared with its Compton
wavelength and compared to any confinement scale in the theory is an unfamiliar
phenomenon, as it does not occur at small . We explore adjoint
trapping further by considering the limit of large J. In particular, for J >>
>> 1, we expect the trapping phenomenon to become unstable.
Using Wilson loop methods, we show that a sharp transition, in which the
generalized quarkonium states become unbound (for massless adjoints) occurs at
. If the adjoint scalars of N=4 are massive and
the theory is confining (as, for instance, in N=1* theories) then the
transition becomes a cross-over, across which the size of the states changes
rapidly from ~ to something of order the confinement scale ~
.Comment: Clarified transition with a better figure and improved presentation;
added careful discussion of the small regime of validity of the
Born-Oppenheimer computation and adjusted some remarks appropriately; also
added two reference
A Three-Flavor AdS/QCD Model with a Back-Reacted Geometry
A fully back-reaction geometry model of AdS/QCD including the strange quark
is described. We find that with the inclusion of the strange quark the impact
on the metric is very small and the final predictions are changed only
negligibly.Comment: 10 pages, 2 figures; references revised, minor change for caption of
fig
On the Couplings of Vector Mesons in AdS/QCD
We address, in the AdS/CFT context, the issue of the universality of the
couplings of the rho meson to other hadrons. Exploring some models, we find
that generically the rho-dominance prediction f_\rho g_{\rho H H}=m_\rho^2 does
not hold, and that g_{\rho H H} is not independent of the hadron H. However, we
prove that, in any model within the AdS/QCD context, there are two limiting
regimes where the g_{\rho H H}, along with the couplings of all excited vector
mesons as well, become H-independent: (1) when H is created by an operator of
large dimension, and (2) when H is a highly-excited hadron. We also find a
sector of a particular model where universality for the rho coupling is exact.
Still, in none of these cases need it be true that f_\rho g_\rho=m_\rho^2,
although we find empirically that the relation does hold approximately (up to a
factor of order two) within the models we have studied.Comment: 28 pages, 3 figures. ver 2: Comments about the commutability of two
universal limits in the D3/D7 case corrected. Typos corrected. ver 3:
Substantive revisions of certain calculations, with improved conventions,
correction of typos, clarifications, new formulas, new figures; no changes in
essential results or conclusion
Thermal Giant Graviton with Non-commutative Dipole Field
Using the type II near-extremal 3D-branes solution we apply the T-duality and
smeared twist to construct the supergravity backgrounds which dual to the 4D
finite temperature non-commutative dipole field theories. We first consider the
zero-temperature system in which, depending on the property of dipole vectors
it may be N=2, N=1 or N=0 theory. We investigate the rotating D3-brane
configurations moving on the spactimes and show that, for the cases of N=2 and
N =1 the rotating D3-brane could be blowed up to the stable spherical
configuration which is called as giant graviton and has a less energy than the
point-like graviton. The giant graviton configuration is stable only if its
angular momentum was less than a critical value of which is an increasing
function of the dipole strength. For the case of non-supersymmetric theory,
however, the spherical configuration has a larger energy than the point-like
graviton. We also find that the dipole field always render the dual giant
graviton to be more stable than the point-like graviton. The relation of dual
giant graviton energy with its angular momentum, which in the AdS/CFT
correspondence being the operator anomalous dimension is obtained. We
furthermore show that the temperature does not change the property of the giant
graviton, while it will render the dual giant graviton to be unstable.Comment: Latex 20 pages, add comments about BPS bound below (3.8
Dynamics of Flux Tubes in Large N Gauge Theories
The gluonic field created by a static quark anti-quark pair is described via
the AdS/CFT correspondence by a string connecting the pair which is located on
the boundary of AdS. Thus the gluonic field in a strongly coupled large N CFT
has a stringy spectrum of excitations. We trace the stability of these
excitations to a combination of large N suppressions and energy conservation.
Comparison of the physics of the N=infinity flux tube in the {\cal N}=4 SYM
theory at weak and strong coupling shows that the excitations are present only
above a certain critical coupling. The density of states of a highly excited
string with a fold reaching towards the horizon of AdS is in exact agreement at
strong coupling with that of the near-threshold states found in a ladder
diagram model of the weak-strong coupling transition. We also study large
distance correlations of local operators with a Wilson loop, and show that the
fall off at weak coupling and N=infinity (i.e. strictly planar diagrams)
matches the strong coupling predictions given by the AdS/CFT correspondence,
rather than those of a weakly coupled U(1) gauge theory.Comment: 22 pages, 4 figures; v2: clarifications in section 5, 1 reference
added; v3: the final version (minor changes, 1 more reference added
Holographic Description of Glueball and Baryon in Noncommutative Dipole Gauge Theory
We study the glueball spectrum in the supersymmetric and non-supersymmetric
4D non-commutative dipole gauge theory from the holographic description. We
adopt the semiclassical WKB approximation to solve the dilaton and
antisymmetric tensor field equations on the dual supergravity backgrounds to
find the analytic formula of the spectrum of and glueballs,
respectively. In the supersymmetric theory we see that the dipole length plays
the intrinsic scale which reflects the discrete spectrum therein. In the
non-supersymmetric theory, the temperature (or the radius of compactification)
in there will now play the intrinsic scale and we see that the dipole has an
effect to produce attractive force between the gluons within the glueball. We
also study the confining force between the quarks within the baryon via strings
that hang into the dipole deformed AdS geometry and see that the dipole could
also produce an attractive force between the quarks. In particular, we find
that the baryon has two phases in which a big baryon is dual to the static
string while a small baryon is described by a moving dual string .Comment: Latex 18 page
Dynamics of false vacuum bubbles: beyond the thin shell approximation
We numerically study the dynamics of false vacuum bubbles which are inside an
almost flat background; we assumed spherical symmetry and the size of the
bubble is smaller than the size of the background horizon. According to the
thin shell approximation and the null energy condition, if the bubble is
outside of a Schwarzschild black hole, unless we assume Farhi-Guth-Guven
tunneling, expanding and inflating solutions are impossible. In this paper, we
extend our method to beyond the thin shell approximation: we include the
dynamics of fields and assume that the transition layer between a true vacuum
and a false vacuum has non-zero thickness. If a shell has sufficiently low
energy, as expected from the thin shell approximation, it collapses (Type 1).
However, if the shell has sufficiently large energy, it tends to expand. Here,
via the field dynamics, field values of inside of the shell slowly roll down to
the true vacuum and hence the shell does not inflate (Type 2). If we add
sufficient exotic matters to regularize the curvature near the shell, inflation
may be possible without assuming Farhi-Guth-Guven tunneling. In this case, a
wormhole is dynamically generated around the shell (Type 3). By tuning our
simulation parameters, we could find transitions between Type 1 and Type 2, as
well as between Type 2 and Type 3. Between Type 2 and Type 3, we could find
another class of solutions (Type 4). Finally, we discuss the generation of a
bubble universe and the violation of unitarity. We conclude that the existence
of a certain combination of exotic matter fields violates unitarity.Comment: 40 pages, 41 figure
Three Flavour QCD from the Holographic Principle
Building on recent research into five-dimensional holographic models of QCD,
we extend this work by including the strange quark with an SU(3)_L\times
SU(3)_R gauge symmetry in the five-dimensional theory. In addition we deform
the naive metric with a single parameter, thereby breaking the conformal
symmetry at low energies. The vector and axial vector sectors are studied in
detail and both the masses and decay constants are calculated with the
additional parameters. It is shown that with a single extra degree of freedom,
exceptional agreement with experimental results can be obtained in the light
quark sector while the kaon sector is found to give around 10% agreement with
lattice results. We propose some simple extensions to this work to be taken up
in future research.Comment: 9 pages, 1 figure, references adde
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