9 research outputs found
The beta function of N=1 SYM in Differential Renormalization
Using differential renormalization, we calculate the complete two-point
function of the background gauge superfield in pure N=1 Supersymmetric
Yang-Mills theory to two loops. Ultraviolet and (off-shell) infrared
divergences are renormalized in position and momentum space respectively. This
allows us to reobtain the beta function from the dependence on the ultraviolet
renormalization scale in an infrared-safe way. The two-loop coefficient of the
beta function is generated by the one-loop ultraviolet renormalization of the
quantum gauge field via nonlocal terms which are infrared divergent on shell.
We also discuss the connection of the beta function to the flow of the
Wilsonian coupling.Comment: 20 pages, 2 figures. Reference added, minor correction
On Penrose Limits and Gauge Theories
We discuss various Penrose limits of conformal and nonconformal backgrounds.
In AdS_5 x T^{1,1}, for a particular choice of the angular coordinate in
T^{1,1} the resulting Penrose limit coincides with the similar limit for AdS_5
x S^5. In this case an identification of a subset of field theory operators
with the string zero modes creation operators is possible. For another limit we
obtain a light-cone string action that resembles a particle in a magnetic
field. We also consider three different types of backgrounds that are dual to
nonconformal field theories: The Schwarzschild black hole in AdS_5, D3-branes
on the small resolution of the conifold and the Klebanov-Tseytlin background.
We find that in all three cases the introduction of nonconformality renders a
theory that is no longer exactly solvable and that the form of the deformation
is universal. The corresponding world sheet theory in the light-cone gauge has
a \tau=x^+ dependent mass term.Comment: 17pp, late
Duality cascades and duality walls
We recast the phenomenon of duality cascades in terms of the Cartan matrix
associated to the quiver gauge theories appearing in the cascade. In this
language, Seiberg dualities for the different gauge factors correspond to Weyl
reflections. We argue that the UV behavior of different duality cascades
depends markedly on whether the Cartan matrix is affine ADE or not. In
particular, we find examples of duality cascades that can't be continued after
a finite energy scale, reaching a "duality wall", in terminology due to M.
Strassler. For these duality cascades, we suggest the existence of a UV
completion in terms of a little string theory.Comment: harvmac, 24 pages, 4 figures. v2: references added. v3: reference
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Bouncing Brane Cosmologies from Warped String Compactifications
We study the cosmology induced on a brane probing a warped throat region in a
Calabi-Yau compactification of type IIB string theory. For the case of a BPS
D3-brane probing the Klebanov-Strassler warped deformed conifold, the cosmology
described by a suitable brane observer is a bouncing, spatially flat
Friedmann-Robertson-Walker universe with time-varying Newton's constant, which
passes smoothly from a contracting to an expanding phase. In the
Klebanov-Tseytlin approximation to the Klebanov-Strassler solution the
cosmology would end with a big crunch singularity. In this sense, the warped
deformed conifold provides a string theory resolution of a spacelike
singularity in the brane cosmology. The four-dimensional effective action
appropriate for a brane observer is a simple scalar-tensor theory of gravity.
In this description of the physics, a bounce is possible because the relevant
energy-momentum tensor can classically violate the null energy condition.Comment: 20 pages, 2 figures; v2, references added and minor correction
Notes on Non-Critical Superstrings in Various Dimensions
We study non-critical superstrings propagating in dimensional
Minkowski space or equivalently, superstrings propagating on the
two-dimensional Euclidean black hole tensored with d-dimensional Minkowski
space. We point out a subtlety in the construction of supersymmetric theories
in these backgrounds, and explain how this does not allow a consistent
geometric interpretation in terms of fields propagating on a cigar-like
spacetime. We explain the global symmetries of the various theories by using
their description as the near horizon geometry of wrapped NS5-brane
configurations. In the six-dimensional theory, we present a CFT description of
the four-dimensional moduli space and the global O(3) symmetry. The worldsheet
action invariant under this symmetry contains both the N=2 sine-Liouville
interaction and the cigar metric, thereby providing an example where the two
interactions are naturally present in the same worldsheet lagrangian already at
the non-dynamical level.Comment: 33 pages, harvma
The Giant Inflaton
We investigate a new mechanism for realizing slow roll inflation in string
theory, based on the dynamics of p anti-D3 branes in a class of mildly warped
flux compactifications. Attracted to the bottom of a warped conifold throat,
the anti-branes then cluster due to a novel mechanism wherein the background
flux polarizes in an attempt to screen them. Once they are sufficiently close,
the M units of flux cause the anti-branes to expand into a fuzzy NS5-brane,
which for rather generic choices of p/M will unwrap around the geometry,
decaying into D3-branes via a classical process. We find that the effective
potential governing this evolution possesses several epochs that can
potentially support slow-roll inflation, provided the process can be arranged
to take place at a high enough energy scale, of about one or two orders of
magnitude below the Planck energy; this scale, however, lies just outside the
bounds of our approximations.Comment: 31 pages, 4 figures, LaTeX. v2: references added, typos fixe
A Soluble String Theory of Hadrons
We consider Penrose limits of the Klebanov-Strassler and Maldacena-Nunez
holographic duals to N =1 supersymmetric Yang-Mills. By focusing in on the IR
region we obtain exactly solvable string theory models. These represent the
nonrelativistic motion and low-lying excitations of heavy hadrons with mass
proportional to a large global charge. We argue that these hadrons, both
physically and mathematically, take the form of heavy nonrelativistic strings;
we term them "annulons." A simple toy model of a string boosted along a compact
circle allows us considerable insight into their properties. We also calculate
the Wilson loop carrying large global charge and show the effect of confinement
is quadratic, not linear, in the string tension.Comment: 40 pages, 1 figure; v2: typos correcte
Cosmic F- and D-strings
Macroscopic fundamental and Dirichlet strings have several potential
instabilities: breakage, tachyon decays, and confinement by axion domain walls.
We investigate the conditions under which metastable strings can exist, and we
find that such strings are present in many models. There are various
possibilities, the most notable being a network of (p,q) strings. Cosmic
strings give a potentially large window into string physics.Comment: 27 pages, 5 figures; v. 5: JHEP style, added comments in section 2.