3,469 research outputs found
Tunneling of Born-Infeld Strings to D2-Branes
A Born-Infeld theory describing a D2-brane coupled to a 4-form RR field
strength is considered, and the general solutions of the static and Euclidean
time equations are derived and discussed. The period of the bounce solutions is
shown to allow a consideration of tunneling and quantum-classical transitions
in the sphaleron region. The order of such transitions, depending on the
strength of the RR field strength, is determined. A criterion is then derived
to confirm these findings.Comment: 20 pages, 7 postscript figures, will appear in NP
On metric geometry of conformal moduli spaces of four-dimensional superconformal theories
Conformal moduli spaces of four-dimensional superconformal theories obtained
by deformations of a superpotential are considered. These spaces possess a
natural metric (a Zamolodchikov metric). This metric is shown to be Kahler. The
proof is based on superconformal Ward identities.Comment: 8 page
Aging and Holography
Aging phenomena are examples of `non-equilibrium criticality' and can be
exemplified by systems with Galilean and scaling symmetries but no time
translation invariance. We realize aging holographically using a deformation of
a non-relativistic version of gauge/gravity duality. Correlation functions of
scalar operators are computed using holographic real-time techniques, and agree
with field theory expectations. At least in this setup, general aging phenomena
are reproduced holographically by complexifying the bulk space-time geometry,
even in Lorentzian signature.Comment: 1 pdf figur
Stabilization of the Yang-Mills chaos in non-Abelian Born-Infeld theory
We investigate dynamics of the homogeneous time-dependent SU(2) Yang-Mills
fields governed by the non-Abelian Born-Infeld lagrangian which arises in
superstring theory as a result of summation of all orders in the string slope
parameter . It is shown that generically the Born-Infeld dynamics is
less chaotic than that in the ordinary Yang-Mills theory, and at high enough
field strength the Yang-Mills chaos is stabilized. More generally, a smothering
effect of the string non-locality on behavior of classical fields is
conjectured.Comment: 7 pages, 5 figure
Mutator Dynamics on a Smooth Evolutionary Landscape
We investigate a model of evolutionary dynamics on a smooth landscape which
features a ``mutator'' allele whose effect is to increase the mutation rate. We
show that the expected proportion of mutators far from equilibrium, when the
fitness is steadily increasing in time, is governed solely by the transition
rates into and out of the mutator state. This results is a much faster rate of
fitness increase than would be the case without the mutator allele. Near the
fitness equilibrium, however, the mutators are severely suppressed, due to the
detrimental effects of a large mutation rate near the fitness maximum. We
discuss the results of a recent experiment on natural selection of E. coli in
the light of our model.Comment: 4 pages, 3 figure
Effects of finite width of excited states on heavy-ion sub-barrier fusion reactions
We discuss the effects of coupling of the relative motion to nuclear
collective excitations which have a finite lifetime on heavy-ion fusion
reactions at energies near and below the Coulomb barrier. Both spreading and
escape widths are explicitly taken into account in the exit doorway model. The
coupled-channels equations are numerically solved to show that the finite
resonance width always hinders fusion cross sections at subbarrier energies
irrespective of the relative importance between the spreading and the escape
widths. We also show that the structure of fusion barrier distribution is
smeared due to the spreading of the strength of the doorway state.Comment: 13 pages, 3 figures, Submitted to Physical Review
Massive higher spins and holography
We review recent progress towards the understanding of higher spin gauge
symmetry breaking in AdS space from a holographic vantage point. According to
the AdS/CFT correspondence, N=4 SYM theory at vanishing coupling constant
should be dual to a theory in AdS which exhibits higher spin gauge symmetry
enhancement. When the SYM coupling is non-zero, all but a handful of HS
currents are violated by anomalies, and correspondingly local higher spin
symmetry in the bulk gets spontaneously broken. In agreement with previous
results and holographic expectations, we find that, barring one notable
exception (spin 1 eating spin 0), the Goldstone modes responsible for HS
symmetry breaking in AdS have non-vanishing mass even in the limit in which the
gauge symmetry is restored. We show that spontaneous breaking a' la
Stueckelberg implies that the mass of the relevant spin s'=s-1 Goldstone field
is exactly the one predicted by the correspondence.Comment: 8 pages, talk presented by M.B. at the "Fourth Meeting on Constrained
Dynamics and Quantum gravity" held in Cala Gonone (Sardinia, Italy),
September 12-16, 200
Corrections to D-brane Action and Generalized Boundary State
In this paper, we generalize a boundary state to the one incorporating
non-constant gauge field strength as an external background coupled to the
boundary of a string worldsheet in bosonic string theory. This newly defined
boundary state satisfies generalized nonlinear boundary conditions with
non-constant gauge field strength, and is BRST invariant. The divergence
immanent in this boundary state coincide with the one calculated in a string
sigma model. We extract the relevant massless part of this generalized boundary
state, and give a part of the D-brane action with the non-constant gauge field
strength, that is, derivative corrections to the D-brane action.Comment: 21 pages, LaTeX, 2 eps figures, a reference added, typos correcte
Scattering of Closed String States from a Quantized D-Particle
By developing an appropriate path-integral formalism, we compute, in bosonic
string theory, the disk amplitude for the scattering of closed string states
from a D-particle, in which the collective coordinate of the D-particle is
fully quantized. As a consequence, the recoil of the D-particle is naturally
taken into account. Our result can be readily factorized in the closed string
channel to yield the boundary state describing the recoiling D-particle. This
turned out to agree with the BRST invariant vertex recently proposed by
Ishibashi to the leading order in the derivative expansion, but it will receive
corrections in subsequent orders. The advantage of our formalism is that it is
extendable to deal with more general processes involving multiple D-particles.
A viewpoint regarding our work as describing a dynamical transition of CFT's is
also discussed.Comment: 24 pages, LaTeX, no figures. Improvements are made on explanations of
the approximation scheme and the handling of the divergenc
Glueball masses in the large N limit
The lowest-lying glueball masses are computed in SU() gauge theory on a
spacetime lattice for constant value of the lattice spacing and for
ranging from 3 to 8. The lattice spacing is fixed using the deconfinement
temperature at temporal extension of the lattice . The calculation is
conducted employing in each channel a variational ansatz performed on a large
basis of operators that includes also torelon and (for the lightest states)
scattering trial functions. This basis is constructed using an automatic
algorithm that allows us to build operators of any size and shape in any
irreducible representation of the cubic group. A good signal is extracted for
the ground state and the first excitation in several symmetry channels. It is
shown that all the observed states are well described by their large
values, with modest corrections. In addition spurious states
are identified that couple to torelon and scattering operators. As a byproduct
of our calculation, the critical couplings for the deconfinement phase
transition for N=5 and N=7 and temporal extension of the lattice are
determined.Comment: 1+36 pages, 22 tables, 21 figures. Typos corrected, conclusions
unchanged, matches the published versio
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