15,070 research outputs found
Strings in Noncommutative Spacetime
Free bosonic strings in noncommutative spacetime are investigated. The string
spectrum is obtained in terms of light-cone quantization. We construct two
different models. In the first model the critical dimension is still required
to be 26 while only extreme high energy spectrum is modified by noncommutative
effect. In the second model, however, the critical dimension is reduced to be
less than 26 while low-energy (massless) spectrum only contains degrees of
freedom of our four dimensional physics.Comment: 9 pages, no figure
Cosmological Constant as Vacuum Energy Density of Quantum Field Theories on Noncommutative Spacetime
We propose a new approach to understand hierarchy problem for cosmological
constant in terms of considering noncommutative nature of space-time. We
calculate that vacuum energy density of the noncommutative quantum field
theories in nontrivial background, which admits a smaller cosmological constant
by introducing an higher noncommutative scale . The result
yields cosmological
constant at the order of current observed value for supersymmetry breaking
scale at 10TeV. It is the same as Banks' phenomenological formula for
cosmological constant.Comment: 7 pages, no figures, v4, references adde
Spinning Strings on Deformed AdS_5 x T^{1,1} with NS B-field
We study classical spinning closed string configuration on logarithmically
deformed AdS_5 x T^{1,1} background with non-trivial Neveu-Schwarz B-field in
which IIB string theory is dual to a non-conformal N=1 SU(N+M) x SU(N) gauge
theory. The integrability on original AdS_5 x T^{1,1} background are
significantly reduced by B-field. We find several spinning string solutions
with two different ansatzs. Solutions for point-like strings and few circular
strings are explicitly obtained. Folded spinning string solutions along radial
direction are shown to be allowed in this background. These solutions exhibit
novel properties and bring some challenges to understand them from dual quantum
field theory.Comment: 26 pages, v.4: The discussions on folded strings was improve
Holography and (1+1)-dimension non-relativistic Quantum Mechanics
I generalize classical gravity/quantum gauge theory duality in AdS/CFT
correspondence to (1+1)-dimensional non-relativistic quantum mechanical system.
It is shown that (1+1)-dimensional non-relativistic quantum mechanical system
can be reproduced from holographic projection of (2+1)-dimension classical
gravity at semiclassical limit. In this explanation every quantum path in
2-dimension corresponds to a classical path of 3-dimension gravity under
definite holographic projection. I consider free particle and harmonic
oscillator as two examples and find their dual gravity description.Comment: 4 pages, no fig, use revtex4.cl
A note on brane/flux annihilation and dS vacua in string theory
We reconsider the dynamics of p anti-D3 branes inside the Klebanov-Strassler
geometry, in which M units of R-R 3-form flux and K units of NS-NS 3-form flux
are presented in deformed conifold. We find that anti-D3 branes blow up into a
spherical D5-brane at weak string coupling via quantum tunnelling. The D5-brane
can be either stable or unstable, depending on number of background flux. The
nucleation rate of D5-brane is suppressed by \exp{-Mp^2}. The classical
mechanically the evolution of unstable D5-brane annihilates one unit of R-R
flux and ends with (K-p) D3-branes. This observation is consistent with one by
Kachru, Pearson and Verlinde, who shew that anti-D3 branes in KS geometry can
blow up into a spherical NS5 brane at strong string coupling, because NS5-brane
is lighter that D5-brane at strong string coupling. We also argue that the
system can end with a meta-stable dS vacuum by fine tuning of number of
background flux.Comment: 14 pages, 3 eps figures, v2: typos modified and references adde
A Deduced Feynman Rule for Calculating Retarded and Advanced Green function in Closed Time Path Formalism
Based on the closed time path formalism, a new Feynman rule for directly
calculating the retarded and advanced Green functions is deduced. This Feynman
rule is used to calculate the two-point self-energy and three-point vertex
correction in theory. The generalized fluctuation-dissipation theorem
for three-point nonlinear response function is verified.Comment: Text and formula are revise
Intersecting branes and adding flavors to the Maldacena-Nunez background
We study adding flavors into the Maldacena-N\u{u}nez background. It is
achieved by introducing spacetime filling D9-branes or intersecting
D5-branes into the background with a wrapping D5-brane. Both D9-branes and
D5-branes can be spacetime filling from the 5D bulk point of view. At the
probe limit it corresponds to introducing non-chiral fundamental flavors into
the dual N=1 SYM. We propose a method to twist the fundamental flavor which has
to involve open string charge. It reflects the fact that coupling fundamental
matter to SYM in the dual string theory corresponds to adding an open string
sectorComment: 16 pages, no figures, use JHEP3.cls, more discussions were adde
Confinement of N=1 Super Yang-Mills from Supergravity
We calculate circular Wilson loop expectation value of pure
super Yang-Mills from the Klebanov-Strassker-Tseytlin solution of supergravity
and the proposed gauge/gravity duality. The calculation is performed
numerically via searching world-sheet minimal surface. It is shown that Wilson
loop exhibits area law for large radius which implies that super
Yang-Mills is confined at large distance or low energy scale. Meanwhile, Wilson
loop exhibits logarithmic behavior for small radius and it indicates
asymptotical freedom of super Yang-Mills at short distance or high
energy scale.Comment: use revtex4.cls, 8 pages, 4 eps fig
Gauge/Gravity Duality, Green Functions of N=2 SYM and Radial/Energy-Scale Relation
We consider supergravity configuration of D5 branes wrapped on supersymmetric
2-cycles and use it to calculate one-point and two-point Green functions of
some special operators in N=2 super Yang-Mills theory. We show that Green
functions obtained from supergravity include two very different parts. One of
them corresponds to perturbative results of quantum field theory, and another
is a non-perturbative effect which corresponds to contribution from instantons
with fractional charge. Comparing Green functions obtained from supergravity
and gauge theory, we obtain radial/energy-scale relation for this gauge/gravity
correspondence with N=2 supersymmetry. This relation leads right beta-function
of N=2 SYM from supergravity configuration.Comment: Latex file, 12 pages, no figures, use JHEP3.cl
Large N_c Expansion in Chiral Quark Model of Mesons
We study SU(3)_L\timesSU(3)_R chiral quark model of mesons up to the next
to leading order of expansion. Composite vector and axial-vector mesons
resonances are introduced via non-linear realization of chiral SU(3) and vector
meson dominant. Effects of one-loop graphs of pseudoscalar, vector and
axial-vector mesons is calculated systematically and the significant results
are obtained. We also investigate correction of quark-gluon coupling and
relationship between chiral quark model and QCD sum rules. Up to powers four of
derivatives, chiral effective lagrangian of mesons is derived and evaluated to
the next to leading order of . Low energy limit of the model is
examined. Ten low energy coupling constants in ChPT are
obtained and agree with ChPT well.Comment: 49 pages, latex file, 6 eps figure
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