1,937 research outputs found
World-sheet Stability of (0,2) Linear Sigma Models
We argue that two-dimensional (0,2) gauged linear sigma models are not
destabilized by instanton generated world-sheet superpotentials. We construct
several examples where we show this to be true. The general proof is based on
the Konishi anomaly for (0,2) theories.Comment: 18 pages, LaTe
Evidenzbasierte Therapie des Raynaud-Syndroms
Zusammenfassung: Das Raynaud-Syndrom ist mit einer Prävalenz von 3-5% ein häufiges klinisches Problem. Dennoch ist die Wirkung der meisten Therapiemöglichkeiten nur unzureichend durch kontrollierte Studien belegt. Zu den Therapien mit höherem Evidenzgrad gehört der Kalziumantagonist Nifedipin, für den in Metaanalysen sowohl bei primärem als auch bei sekundärem Raynaud-Syndrom eine verbesserte periphere Durchblutung sowie eine Abnahme der Frequenz und des Schweregrades der Raynaud-Attacken nachgewiesen werden konnte. Ähnliches gilt für intravenös appliziertes Iloprost in der Therapie des sekundären Raynaud-Syndroms bei systemischer Sklerose. Intravenös verabreichtes Iloprost verbessert darüber hinaus das Abheilen von Fingerkuppenulzera bei Patienten mit systemischer Sklerose. Vielversprechende Therapieansätze stellen Angiotensin-II-Rezeptor-1-Antagonisten (Losartan), die Kalziumantagonisten Felodipin und Amlodipin, Serotonin-Reuptake-Hemmer (Fluoxetin) und Phosphodiesterase-V-Hemmer (Sildenafil, Vardenafil) dar, die sich in kontrollierten Einzelstudien als wirksam erwiesen haben. Jedoch fehlen Erfahrungen mit größeren Patientenzahlen und längeren Anwendungszeiten, um diese Therapiemöglichkeiten abschließend zu beurteile
Deformed Quantum Cohomology and (0,2) Mirror Symmetry
We compute instanton corrections to correlators in the genus-zero topological
subsector of a (0,2) supersymmetric gauged linear sigma model with target space
P1xP1, whose left-moving fermions couple to a deformation of the tangent
bundle. We then deduce the theory's chiral ring from these correlators, which
reduces in the limit of zero deformation to the (2,2) ring. Finally, we compare
our results with the computations carried out by Adams et al.[ABS04] and Katz
and Sharpe[KS06]. We find immediate agreement with the latter and an
interesting puzzle in completely matching the chiral ring of the former.Comment: AMSLatex, 30 pages, one eps figure. V4: typos corrected, final
version appearing in JHE
Interpreting the M2-brane Action
The world-volume theory of multiple M2-branes proposed recently has a free
scalar field. For large vev of this scalar field the world-volume action
reduces to that of multiple D2-branes with Yang-Mills coupling proportional to
the vev. We suggest that the correct interpretation of this scalar field is as
the radial position of the M2-brane center of mass in a cylindrical polar
coordinate system. Regarding the azimuthal angle as compact we can regard this
as a set of coincident D2-branes in type IIA string theory with varying dilaton
and metric. We find that the effective world-volume theory on the D2-branes has
Yang-Mills coupling proportional to the radial coordinate; furthermore the
radial coordinate satisfies free field equations of motion. This agrees with
the corresponding results derived from the M2-brane world-volume theory.Comment: LaTeX file, 6 page
Continuum Annulus Amplitude from the Two-Matrix Model
An explicit expression for continuum annulus amplitudes having boundary
lengths and is obtained from the two-matrix model for the
case of the unitary series; . In the limit of vanishing
cosmological constant, we find an integral representation of these amplitudes
which is reproduced, for the cases of the and the , by a continuum approach consisting of quantum mechanics of loops
and a matter system integrated over the modular parameter of the annulus. We
comment on a possible relation to the unconventional branch of the Liouville
gravity.Comment: 9 pages, OU-HET 190, revised version. A part of the conclusions has
been corrected. A new result on integral representation of the annulus
amplitudes has been adde
F-theory and linear sigma models
We present an explicit method for translating between the linear sigma model
and the spectral cover description of SU(r) stable bundles over an elliptically
fibered Calabi-Yau manifold. We use this to investigate the 4-dimensional
duality between (0,2) heterotic and F-theory compactifications. We indirectly
find that much interesting heterotic information must be contained in the
`spectral bundle' and in its dual description as a gauge theory on multiple
F-theory 7-branes.
A by-product of these efforts is a method for analyzing semistability and the
splitting type of vector bundles over an elliptic curve given as the sheaf
cohomology of a monad.Comment: 40 pages, no figures; minor cosmetic reorganization of section 4;
reference [6] update
Comments on Supersymmetric Vector and Matrix Models
Some results in random matrices are generalized to supermatrices, in
particular supermatrix integration is reduced to an integration over the
eigenvalues and the resulting volume element is shown to be equivalent to a one
dimensional Coulomb gas of both positive and negative charges.It is shown
that,for polynomial potentials, after removing the instability due to the
annihilation of opposite charges, supermatrix models are indistinguishable from
ordinary matrix models, in agreement with a recent result by Alvarez-Gaume and
Manes. It is pointed out however that this may not be true for more general
potentials such as for instance the supersymmetric generalization of the Penner
model.Comment: 6 page
On the validity of ADM formulation in 2D quantum gravity
We investigate 2d gravity quantized in the ADM formulation, where only the
loop length is retained as a dynamical variable of the gravitation, in
order to get an intuitive physical insight of the theory. The effective action
of is calculated by adding scalar fields of conformal coupling, and the
problems of the critical dimension and the time development of are
addressed.Comment: 12 page
An Exact Solution to O(26) Sigma Model coupled to 2-D Gravity
By a mapping to the bosonic string theory, we present an exact solution to
the O(26) sigma model coupled to 2-D quantum gravity. In particular, we obtain
the exact gravitational dressing to the various matter operators classified by
the irreducible representations of O(26). We also derive the exact form of the
gravitationally modified beta function for the original coupling constant
. The relation between our exact solution and the asymptotic solution
given in ref[3] is discussed in various aspects.Comment: 10 pages, pupt-144
Landscape Study of Target Space Duality of (0,2) Heterotic String Models
In the framework of (0,2) gauged linear sigma models, we systematically
generate sets of perturbatively dual heterotic string compactifications. This
target space duality is first derived in non-geometric phases and then
translated to the level of GLSMs and its geometric phases. In a landscape
analysis, we compare the massless chiral spectra and the dimensions of the
moduli spaces. Our study includes geometries given by complete intersections of
hypersurfaces in toric varieties equipped with SU(n) vector bundles defined via
the monad construction.Comment: 40 pages, 6 figure
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