33 research outputs found
Fundamental Strings and Black Holes
We propose a black hole thermodynamic description of highly excited charged
and uncharged perturbative string states in 3+1 dimensional type II and 4+1
dimensional heterotic string theory. We also discuss the generalization to
extremal and non-extremal black holes carrying magnetic charges.Comment: 25 pages, harvmac; V2: Added reference
Central Charges and Symmetries in Super Yang-Mills
We use recent results of Intriligator and Wecht [hep-th/0304128] to study the
phase structure of \NN=1 super Yang-Mills theory with gauge group ,
a chiral superfield in the adjoint, and chiral superfields in the
fundamental representation of the gauge group. Our discussion sheds new light
on [hep-th/0304128] and supports the conjecture that the central charge
decreases under RG flows and is non-negative in unitary four dimensional
conformal field theories.Comment: 35 pages, 14 figures; harvma
D-branes and SQCD in Non-Critical Superstring Theory
Using exact boundary conformal field theory methods we analyze the D-brane
physics of a specific four-dimensional non-critical superstring theory which
involves the N=2 SL(2)/U(1) Kazama-Suzuki model at level 1. Via the holographic
duality of hep-th/9907178 our results are relevant for D-brane dynamics in the
background of NS5-branes and D-brane dynamics near a conifold singularity. We
pay special attention to a configuration of D3- and D5-branes that realizes N=1
supersymmetric QCD and discuss the massless spectrum and classical moduli of
this setup in detail. We also comment briefly on the implications of this
construction for the recently proposed generalization of the AdS/CFT
correspondence by Klebanov and Maldacena within the setting of non-critical
superstrings.Comment: harvmac, 47 pages, 6 figures; v4 same as v3 due to submission erro
Universality of Nonperturbative Effects in c<1 Noncritical String Theory
Nonperturbative effects in c<1 noncritical string theory are studied using
the two-matrix model. Such effects are known to have the form fixed by the
string equations but the numerical coefficients have not been known so far.
Using the method proposed recently, we show that it is possible to determine
the coefficients for (p,q) string theory. We find that they are indeed finite
in the double scaling limit and universal in the sense that they do not depend
on the detailed structure of the potential of the two-matrix model.Comment: 17 page
Non-critical Heterotic Superstrings in Various Dimensions
We construct heterotic string theories on spacetimes of the form R^{d-1,1}
times N=2 linear dilaton, where d=6,4,2,0. There are two lines of
supersymmetric theories descending from the two supersymmetric ten-dimensional
heterotic theories. These have gauge groups which are lower rank subgroups of
E_{8} times E_{8} and SO(32). On turning on a (2,2) deformation which makes the
two dimensional part a smooth SL_{2}(R)/U(1) supercoset, the gauge groups get
broken further. In the deformed theories, there are non-trivial moduli which
are charged under the surviving gauge group in the case of d=6. We construct
the marginal operators on the worldsheet corresponding to these moduli.Comment: 27 pages, harvmac. v2 reference adde
More on Superstrings in AdS(3) x N
We study superstring theories on AdS(3) x N backgrounds yielding N=2,3,4
extended superconformal symmetries in the dual boundary CFT. In each case the
necessary constraints on the internal worldsheet theory N are found.Comment: JHEP style, 22 pages; v2: new references and a couple of sentences on
N=1 are adde
Power-Law Inflation from the Rolling Tachyon
Modeling the potential by an inverse square law in terms of the tachyon field
() we find exact solution for spatially flat isotropic
universe.We show that for the model undergoes power-law
inflation. A way to construct other exact solutions is specified and
exemplified.Comment: References added. Matches the version in print. To appear in PR
c=1 Matrix Models: Equivalences and Open-Closed String Duality
We give an explicit demonstration of the equivalence between the Normal
Matrix Model (NMM) of c=1 string theory at selfdual radius and the
Kontsevich-Penner (KP) model for the same string theory. We relate macroscopic
loop expectation values in the NMM to condensates of the closed string tachyon,
and discuss the implications for open-closed duality. As in c<1, the
Kontsevich-Miwa transform between the parameters of the two theories appears to
encode open-closed string duality, though our results also exhibit some
interesting differences with the c<1 case. We also briefly comment on two
different ways in which the Kontsevich model originates.Comment: 27 pages, latex, 1 figure, typos, discussion added, acknowledgements
update
Lessons from : Vacuum structure, Asymptotic Series, Instantons and all that
We discuss two dimensional with fermions in the
fundamental as well as adjoint representation. We find factorial growth in the coefficients of
the large order perturbative expansion. We argue that this behavior is related
to classical solutions of the theory, instantons, thus it has nonperturbative
origin. Phenomenologically such a growth is related to highly excited states in
the spectrum. We also analyze the heavy-light quark system within
operator product expansion (which it turns out to be an asymptotic series).
Some vacuum condensates \la\bar{q}(x_{\mu}D_{\mu})^{2n}q\ra\sim (x^2)^n\cdot
n! which are responsible for this factorial growth are also discussed. We
formulate some general puzzles which are not specific for 2D physics, but are
inevitable features of any asymptotic expansion. We resolve these apparent
puzzles within and we speculate that analogous puzzles might occur in
real 4-dimensional QCD as well.Comment: latex, 26 pages. A final version to appear in Phys. Rev.
Tachyon Condensation, Open-Closed Duality, Resolvents, and Minimal Bosonic and Type 0 Strings
Type 0A string theory in the (2,4k) superconformal minimal model backgrounds
and the bosonic string in the (2,2k-1) conformal minimal models, while
perturbatively identical in some regimes, may be distinguished
non-perturbatively using double scaled matrix models. The resolvent of an
associated Schrodinger operator plays three very important interconnected
roles, which we explore perturbatively and non-perturbatively. On one hand, it
acts as a source for placing D-branes and fluxes into the background, while on
the other, it acts as a probe of the background, its first integral yielding
the effective force on a scaled eigenvalue. We study this probe at disc, torus
and annulus order in perturbation theory, in order to characterize the effects
of D-branes and fluxes on the matrix eigenvalues. On a third hand, the
integrated resolvent forms a representation of a twisted boson in an associated
conformal field theory. The entire content of the closed string theory can be
expressed in terms of Virasoro constraints on the partition function, which is
realized as wavefunction in a coherent state of the boson. Remarkably, the
D-brane or flux background is simply prepared by acting with a vertex operator
of the twisted boson. This generates a number of sharp examples of open-closed
duality, both old and new. We discuss whether the twisted boson conformal field
theory can usefully be thought of as another holographic dual of the
non-critical string theory.Comment: 37 pages, some figures, LaTe