3,578 research outputs found
Effective superpotentials for B-branes in Landau-Ginzburg models
We compute the partition function for the topological Landau-Ginzburg B-model
on the disk. This is done by treating the worldsheet superpotential
perturbatively. We argue that this partition function as a function of bulk and
boundary perturbations may be identified with the effective D-brane
superpotential in the target spacetime. We point out the relationship of this
approach to matrix factorizations. Using these methods, we prove a conjecture
for the effective superpotential of Herbst, Lazaroiu and Lerche for the A-type
minimal models. We also consider the Landau-Ginzburg theory of the cubic torus
where we show that the effective superpotential, given by the partition
function, is consistent with the one obtained by summing up disk instantons in
the mirror A-model. This is done by explicitly constructing the open-string
mirror map.Comment: 57p, 7 figs, harvma
Fluctuations and the QCD phase diagram
In this contribution the role of quantum fluctuations for the QCD phase
diagram is discussed. This concerns in particular the importance of the matter
back-reaction to the gluonic sector. The impact of these fluctuations on the
location of the confinement/deconfinement and the chiral transition lines as
well as their interrelation are investigated. Consequences of our findings for
the size of a possible quarkyonic phase and location of a critical endpoint in
the phase diagram are drawn.Comment: 7 pages, 3 figures, to appear in Physics of Atomic Nucle
The matrix factorisations of the D-model
The fundamental matrix factorisations of the D-model superpotential are found
and identified with the boundary states of the corresponding conformal field
theory. The analysis is performed for both GSO-projections. We also comment on
the relation of this analysis to the theory of surface singularities and their
orbifold description.Comment: 23 pages, LaTe
Equivalences between GIT quotients of Landau-Ginzburg B-models
We define the category of B-branes in a (not necessarily affine)
Landau-Ginzburg B-model, incorporating the notion of R-charge. Our definition
is a direct generalization of the category of perfect complexes. We then
consider pairs of Landau-Ginzburg B-models that arise as different GIT
quotients of a vector space by a one-dimensional torus, and show that for each
such pair the two categories of B-branes are quasi-equivalent. In fact we
produce a whole set of quasi-equivalences indexed by the integers, and show
that the resulting auto-equivalences are all spherical twists.Comment: v3: Added two references. Final version, to appear in Comm. Math.
Phy
D-branes in Toroidal Orbifolds and Mirror Symmetry
We study D-branes extended in T^2/Z_4 using the mirror description as a
tensor product of minimal models. We describe branes in the mirror both as
boundary states in minimal models and as matrix factorizations in the
corresponding Landau-Ginzburg model. We isolate a minimal set of branes and
give a geometric interpretation of these as D1-branes constrained to the
orbifold fixed points. This picture is supported both by spacetime arguments
and by the explicit construction of the boundary states, adapting the known
results for rational boundary states in the minimal models. Similar techniques
apply to a larger class of toroidal orbifolds.Comment: 30 pages, 2 figure
Triangle-generation in topological D-brane categories
Tachyon condensation in topological Landau-Ginzburg models can generally be
studied using methods of commutative algebra and properties of triangulated
categories. The efficiency of this approach is demonstrated by explicitly
proving that every D-brane system in all minimal models of type ADE can be
generated from only one or two fundamental branes.Comment: 34 page
Herschel observations of interstellar chloronium. II - Detections toward G29.96-0.02, W49N, W51, and W3(OH), and determinations of the ortho-to-para and Cl/Cl isotopic ratios
We report additional detections of the chloronium molecular ion, HCl,
toward four bright submillimeter continuum sources: G29.96, W49N, W51, and
W3(OH). With the use of the HIFI instrument on the Herschel Space Observatory,
we observed the transition of ortho-HCl at 781.627
GHz in absorption toward all four sources. Much of the detected absorption
arises in diffuse foreground clouds that are unassociated with the background
continuum sources and in which our best estimates of the ratio lie in the range .
These chloronium abundances relative to atomic hydrogen can exceed the
predictions of current astrochemical models by up to a factor of 5. Toward
W49N, we have also detected the transition of
ortho-HCl at 780.053 GHz and the transition of
para-HCl at 485.418 GHz. These observations imply column density ratios that are consistent with the
solar system Cl/Cl isotopic ratio of 3.1, and chloronium
ortho-to-para ratios consistent with 3, the ratio of spin statistical weights.Comment: 31 pages, including 7 figures. Accepted for publication in the Ap
D-brane superpotentials and RG flows on the quintic
The behaviour of D2-branes on the quintic under complex structure
deformations is analysed by combining Landau-Ginzburg techniques with methods
from conformal field theory. It is shown that the boundary renormalisation
group flow induced by the bulk deformations is realised as a gradient flow of
the effective space time superpotential which is calculated explicitly to all
orders in the boundary coupling constant.Comment: 24 pages, 1 figure, v2:Typo in (3.14) correcte
The model of dynamo with small number of modes and magnetic activity of T Tauri stars
The model that describes operation of dynamo in fully convective stars is
presented. It is based on representation of stellar magnetic field as a
superposition of finite number of poloidal and toroidal free damping modes. In
the frame of adopted low of stellar differential rotation we estimated minimal
value of dynamo number D, starting from which generation of cyclic magnetic
field in stars without radiative core is possible. We also derived expression
for period of the cycle. It was found that dynamo cycles of fully convective
stars and stars with thin convective envelopes differ in a qualitative way: 1)
distribution of spots over latitude during the cycle is different in these
stars; 2) the model predicts that spot formation in fully convective stars
should be strongly suppressed at some phases of the cycle.
We have analyzed historical lightcurve of WTTS star V410 Tau and found that
long term activity of the star is not periodic process. Rather one can speak
about quasi cyclic activity with characteristic time of yr and chaotic
component over imposed. We concluded also that redistribution of cool spots
over longitude is the reason of long term variations of V410 Tau brightness. It
means that one can not compare directly results of photometric observations
with predictions of our axially symmetric (for simplicity) model which allows
to investigate time evolution of spot's distribution over latitude. We then
discuss what kind of observations and in which way could be used to check
predictions of the dynamo theory.Comment: 18 pages, 5 figures, accepted to Astron. Let
Sulphur-bearing molecules in diffuse molecular clouds: new results from SOFIA/GREAT and the IRAM 30 m telescope
We have observed five sulphur-bearing molecules in foreground diffuse
molecular clouds lying along the sight-lines to five bright continuum sources.
We have used the GREAT instrument on SOFIA to observe the 1383 GHz transitions of SH towards the star-forming regions W31C,
G29.96-0.02, G34.3+0.1, W49N and W51, detecting foreground absorption towards
all five sources; and the EMIR receivers on the IRAM 30m telescope at Pico
Veleta to detect the HS 1(10)-1(01), CS J=2-1 and SO 3(2)-2(1) transitions.
In nine foreground absorption components detected towards these sources, the
inferred column densities of the four detected molecules showed relatively
constant ratios, with N(SH)/N(HS) in the range 1.1 - 3.0, N(CS)/N(HS)
in the range 0.32 - 0.61, and N(SO)/N(HS) in the range 0.08 - 0.30. The
observed SH/H ratios - in the range (0.5-2.6) - indicate
that SH (and other sulphur-bearing molecules) account for << 1% of the
gas-phase sulphur nuclei. The observed abundances of sulphur-bearing molecules,
however, greatly exceed those predicted by standard models of cold diffuse
molecular clouds, providing further evidence for the enhancement of endothermic
reaction rates by elevated temperatures or ion-neutral drift. We have
considered the observed abundance ratios in the context of shock and turbulent
dissipation region (TDR) models. Using the TDR model, we find that the
turbulent energy available at large scale in the diffuse ISM is sufficient to
explain the observed column densities of SH and CS. Standard shock and TDR
models, however, fail to reproduce the column densities of HS and SO by a
factor of about 10; more elaborate shock models - in which account is taken of
the velocity drift, relative to H, of SH molecules produced by the
dissociative recombination of HS - reduce this discrepancy to a factor
~ 3.Comment: 30 pages, accepted for publication in A&
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