25 research outputs found
Light-Cone Wilson Loops and the String/Gauge Correspondence
We investigate a \Pi-shape Wilson loop in N=4 super Yang--Mills theory, which
lies partially at the light-cone, and consider an associated open superstring
in AdS_5 x S^5. We discuss how this Wilson loop determines the anomalous
dimensions of conformal operators with large Lorentz spin and present an
explicit calculation in perturbation theory to order \lambda. We find the
minimal surface in the supergravity approximation, that reproduces the Gubser,
Klebanov and Polyakov prediction for the anomalous dimensions at large
\lambda=g_YM^2 N, and discuss its quantum-mechanical interpretation.Comment: 17pp., Latex, 4 figures; v.2: factors of 2 put righ
Thermodynamics of D0-branes in matrix theory
We examine the matrix theory representation of D0-brane dynamics at finite
temperature. In this case, violation of supersymmetry by temperature leads to a
non-trivial static potential between D0-branes at any finite temperature. We
compute the static potential in the 1-loop approximation and show that it is
short-ranged and attractive. We compare the result with the computations in
superstring theory. We show that thermal states of D0-branes can be reproduced
by matrix theory only when certain care is taken in integration over the moduli
space of classical solutions in compactified time.Comment: 13 pages, 1 figur
Zig Zag symmetry in AdS/CFT duality
The validity of the Bianchi identity, which is intimately connected with the
zig zag symmetry, is established, for piecewise continuous contours, in the
context of Polakov's gauge field-string connection in the large 'tHooft
coupling limit, according to which the chromoelectric `string' propagates in
five dimensions with its ends attached on a Wilson loop in four dimensions. An
explicit check in the wavy line approximation is presented.Comment: 24 pages version to appear in EPJ
On noncommutative vacua and noncommutative solitons
We consider noncommutative theory of a compact scalar field. The recently
discovered projector solitons are interpreted as classical vacua in the model
considered. Localized solutions to the projector equation are pointed out and
their brane interpretation is discussed. An example of the noncommutative
soliton interpolating between such vacua is given. No strong noncommutativity
limit is assumed.Comment: 9 pages, latex, references adde
Twisted Eguchi-Kawai Reduced Chiral Models
We study the twisted Eguchi-Kawai (TEK) reduction procedure for large-N
unitary matrix lattice models. In particular, we consider the case of
two-dimensional principal chiral models, and use numerical Monte Carlo (MC)
simulations to check the conjectured equivalence of TEK reduced model and
standard lattice model in the large-N limit. The MC results are compared with
the large-N limit of lattice principal chiral models to verify the supposed
equivalence. The consistency of the TEK reduction procedure is verified in the
strong-coupling region, i.e. for where is the
location of the large-N phase transition. On the other hand, in the
weak-coupling regime , relevant for the continuum limit, our MC
results do not support the equivalence of the large-N limits of the lattice
chiral model and the corresponding TEK reduction. The implications for the
correspondence between TEK model and noncommutative field theory are also
discussed.Comment: 16 page
Wilson Loops, D-Branes, and Reparametrization Path-Integrals
We study path-integrals over reparametrizations of the world-sheet boundary.
Such integrals arise when string propagates between fixed space-time contours.
In gauge/string duality they are needed to describe gauge theory Wilson loops.
We show that (1) in AdS/CFT, the integral is well defined and gives a finite
1-loop correction to the Wilson loop; (2) in critical string theory, the
integral is UV divergent, and fixed contour amplitudes are off shell. In the
second case, we show that the divergences can be removed by renormalizing the
contour. We calculate the 2-loop contour beta-function and explain how it is
related to the D0-brane effective action. We also apply this method to compute
the first alpha' correction to the effective action of higher dimensional
branes.Comment: 36p
Sudakov Resummation for Subleading SCET Currents and Heavy-to-Light Form Factors
The hard-scattering contributions to heavy-to-light form factors at large
recoil are studied systematically in soft-collinear effective theory (SCET).
Large logarithms arising from multiple energy scales are resummed by matching
QCD onto SCET in two stages via an intermediate effective theory. Anomalous
dimensions in the intermediate theory are computed, and their form is shown to
be constrained by conformal symmetry. Renormalization-group evolution equations
are solved to give a complete leading-order analysis of the hard-scattering
contributions, in which all single and double logarithms are resummed. In two
cases, spin-symmetry relations for the soft-overlap contributions to form
factors are shown not to be broken at any order in perturbation theory by
hard-scattering corrections. One-loop matching calculations in the two
effective theories are performed in sample cases, for which the relative
importance of renormalization-group evolution and matching corrections is
investigated. The asymptotic behavior of Sudakov logarithms appearing in the
coefficient functions of the soft-overlap and hard-scattering contributions to
form factors is analyzed.Comment: 50 pages, 10 figures; minor corrections, version to appear in JHE
Nonforward anomalous dimensions of Wilson operators in N=4 super-Yang-Mills theory
We present the next-to-leading order results for universal non-forward
anomalous dimensions of Wilson twist-2 operators in N=4 supersymmetric
Yang-Mills theory. The whole calculation was performed using supersymmetric
Ward identities derived in this paper together with already known QCD results
and does not involve any additional calculation of diagrams. We also considered
one particular limit of our result, which could potentially be interesting in
the context of AdS/CFT correspondence.Comment: 15 pages, references added, typos corrected, version accepted in JHE
Non-perturbative equivalences among large N gauge theories with adjoint and bifundamental matter fields
We prove an equivalence, in the large N limit, between certain U(N) gauge
theories containing adjoint representation matter fields and their orbifold
projections. Lattice regularization is used to provide a non-perturbative
definition of these theories; our proof applies in the strong coupling, large
mass phase of the theories. Equivalence is demonstrated by constructing and
comparing the loop equations for a parent theory and its orbifold projections.
Loop equations for both expectation values of single-trace observables, and for
connected correlators of such observables, are considered; hence the
demonstrated non-perturbative equivalence applies to the large N limits of both
string tensions and particle spectra.Comment: 40 pages, JHEP styl
High Energy QCD: Stringy Picture from Hidden Integrability
We discuss the stringy properties of high-energy QCD using its hidden
integrability in the Regge limit and on the light-cone. It is shown that
multi-colour QCD in the Regge limit belongs to the same universality class as
superconformal =2 SUSY YM with at the strong coupling
orbifold point. The analogy with integrable structure governing the low energy
sector of =2 SUSY gauge theories is used to develop the brane picture
for the Regge limit. In this picture the scattering process is described by a
single M2 brane wrapped around the spectral curve of the integrable spin chain
and unifying hadrons and reggeized gluons involved in the process. New
quasiclassical quantization conditions for the complex higher integrals of
motion are suggested which are consistent with the duality of the
multi-reggeon spectrum. The derivation of the anomalous dimensions of the
lowest twist operators is formulated in terms of the Riemann surfacesComment: 37 pages, 3 figure