544 research outputs found
Chiral Symmetry in Charmonium - Pion Cross Section
We perform a non-perturbative calculation of the cross section
using a effective Lagrangian. Our results differ from those
of previous calculations, specially in the description of vertices involving
pions.Comment: 6 pages, RevTeX including 2 figures in eps file
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
adde
Phases and geometry of the N=1 A_2 quiver gauge theory and matrix models
We study the phases and geometry of the N=1 A_2 quiver gauge theory using
matrix models and a generalized Konishi anomaly. We consider the theory both in
the Coulomb and Higgs phases. Solving the anomaly equations, we find that a
meromorphic one-form sigma(z)dz is naturally defined on the curve Sigma
associated to the theory. Using the Dijkgraaf-Vafa conjecture, we evaluate the
effective low-energy superpotential and demonstrate that its equations of
motion can be translated into a geometric property of Sigma: sigma(z)dz has
integer periods around all compact cycles. This ensures that there exists on
Sigma a meromorphic function whose logarithm sigma(z)dz is the differential. We
argue that the surface determined by this function is the N=2 Seiberg-Witten
curve of the theory.Comment: 41 pages, 2 figures, JHEP style. v2: references adde
J/psi couplings to charmed resonances and to pi
We present an evaluation of the strong couplings JD^(*)D^(*) and
JD^(*)D^(*)pi by an effective field theory of quarks and mesons. These
couplings are necessary to calculate pi+J/psi --> D^(*)+barD^(*) cross
sections, an important background to the J/psi suppression signal in the
quark-gluon plasma. We write down the general effective lagrangian and compute
the relevant couplings in the soft pion limit and beyond.Comment: 11 pages, 4 figures, 2 reference added and minor comments, style
changed to RevTe
Quasars as Probes of Late Reionization and Early Structure Formation
Observations of QSOs at z ~ 5.7 - 6.4 show the appearance of Gunn-Peterson
troughs around z ~ 6, and a change in the slope of the IGM optical depth tau(z)
near z ~ 5.5. These results are interpreted as a signature of the end of the
reionization era, which probably started at considerably higher redshifts.
However, there also appears to be a substantial cosmic variance in the
transmission of the IGM, both along some lines of sight, and among different
lines of sight, in this intriguing redshift regime. We suggest that this is
indicative of a spatially uneven reionization, possibly caused by the
bias-driven primordial clustering of the reionization sources. There is also
some independent evidence for a strong clustering of QSOs at z ~ 4 - 5 and
galaxies around them, supporting the idea of the strong biasing of the first
luminous sources at these redshifts. Larger samples of high-z QSOs are needed
in order to provide improved, statistically significant constraints for the
models of these phenomena. We expect that the Palomar-Quest (PQ) survey will
soon provide a new set of QSOs to be used as cosmological probes in this
redshift regime.Comment: To appear in proceedings of UC Irvine May 2005 workshop on "First
Light & Reionization", eds. E. Barton & A. Cooray, New Astronomy Reviews, in
pres
(Anti)symmetric matter and superpotentials from IIB orientifolds
We study the IIB engineering of N=1 gauge theories with unitary gauge group
and matter in the adjoint and (anti)symmetric representations. We show that
such theories can be obtained as Z2 orientifolds of Calabi-Yau A2 fibrations,
and discuss the explicit T-duality transformation to an orientifolded
Hanany-Witten construction. The low energy dynamics is described by a geometric
transition of the orientifolded background. Unlike previously studied cases, we
show that the orientifold 5-`plane' survives the transition, thus bringing a
nontrivial contribution to the effective superpotential. We extract this
contribution by using matrix model results and compare with geometric data. A
Higgs branch of our models recovers the engineering of SO/Sp theories with
adjoint matter through an O5-`plane' T-dual to an O6-plane. We show that the
superpotential agrees with that produced by engineering through an O5-`plane'
dual to an O4-plane, even though the orientifold of this second construction is
replaced by fluxes after the transition.Comment: 40 page
Quivers via anomaly chains
We study quivers in the context of matrix models. We introduce chains of
generalized Konishi anomalies to write the quadratic and cubic equations that
constrain the resolvents of general affine and non-affine quiver gauge
theories, and give a procedure to calculate all higher-order relations. For
these theories we also evaluate, as functions of the resolvents, VEV's of
chiral operators with two and four bifundamental insertions. As an example of
the general procedure we explicitly consider the two simplest quivers A2 and
A1(affine), obtaining in the first case a cubic algebraic curve, and for the
affine theory the same equation as that of U(N) theories with adjoint matter,
successfully reproducing the RG cascade result.Comment: 32 pages, latex; typos corrected, published versio
Orbiting Membranes in M-theory on AdS_7 x S^4 Background
We study classical solutions describing rotating and boosted membranes on
AdS_7 x S^4 background in M-theory. We find the dependence of the energy on the
spin and R-charge of these solutions. In the flat space limit we get E ~
S^{2/3}, while for AdS at leading order E-S grows as S^{1/3}. The membranes on
AdS_4 x S^7 background have briefly been studied as well.Comment: 13 pages, latex, v2: a note and refs. added, some typos correcte
Progress in the determination of the cross section
Improving previous calculations, we compute the cross section using QCD sum rules. Our sum rules for the , , and hadronic
matrix elements are constructed by using vaccum-pion correlation functions, and
we work up to twist-4 in the soft-pion limit. Our results suggest that, using
meson exchange models is perfectly acceptable, provided that they include form
factors and that they respect chiral symmetry. After doing a thermal average we
get mb at T=150\MeV.Comment: 22 pages, RevTeX4 including 7 figures in ps file
Chiral field theories, Konishi anomalies and matrix models
We study a chiral N=1, U(N) field theory in the context of the Dijkgraaf-Vafa
correspondence. Our model contains one adjoint, one conjugate symmetric and one
antisymmetric chiral multiplet, as well as eight fundamentals. We compute the
generalized Konishi anomalies and compare the chiral ring relations they induce
with the loop equations of the (intrinsically holomorphic) matrix model defined
by the tree-level superpotential of the field theory. Surprisingly, we find
that the matrix model is well-defined only if the number of flavors equals two!
Despite this mismatch, we show that the 1/N expansion of the loop equations
agrees with the generalized Konishi constraints. This indicates that the matrix
model - gauge theory correspondence should generally be modified when applied
to theories with net chirality. We also show that this chiral theory produces
the same gaugino superpotential as a nonchiral SO(N) model with a single
symmetric multiplet and a polynomial superpotential.Comment: 43 page
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