24,969 research outputs found
Mirror Symmetry for Calabi-Yau Hypersurfaces in Weighted P_4 and Extensions of Landau Ginzburg Theory
Recently two groups have listed all sets of weights (k_1,...,k_5) such that
the weighted projective space P_4^{(k_1,...,k_5)} admits a transverse
Calabi-Yau hypersurface. It was noticed that the corresponding Calabi-Yau
manifolds do not form a mirror symmetric set since some 850 of the 7555
manifolds have Hodge numbers (b_{11},b_{21}) whose mirrors do not occur in the
list. By means of Batyrev's construction we have checked that each of the 7555
manifolds does indeed have a mirror. The `missing mirrors' are constructed as
hypersurfaces in toric varieties. We show that many of these manifolds may be
interpreted as non-transverse hypersurfaces in weighted P_4's, ie,
hypersurfaces for which dp vanishes at a point other than the origin. This
falls outside the usual range of Landau--Ginzburg theory. Nevertheless
Batyrev's procedure provides a way of making sense of these theories.Comment: 29 pages, plain TeX. Two figures submitted separately as a uuencoded
file. A plot at the end of the paper requires an extended memory version of
TeX. Instructions for suppressing the plot included at head of source fil
Three Dimensional N=2 Gauge Theories and Degenerations of Calabi-Yau Four-Folds
Three dimensional N=2 gauge theories with arbitrary gauge group and
fundamental flavors are engineered from degenerations of Calabi-Yau four-folds.
We show how Coulomb and Higgs branches emerge in the geometric picture. The
analysis of instanton generated superpotentials unravels interesting aspects of
the five-brane effective action in M theory.Comment: subsections on Sp(N) and Spin(2N+1) theories removed, 32 pages,
harvmac, 6 postscript figure
Vacuum field energy and spontaneous emission in anomalously dispersive cavities
Anomalously dispersive cavities, particularly white light cavities, may have
larger bandwidth to finesse ratios than their normally dispersive counterparts.
Partly for this reason, their use has been proposed for use in LIGO-like
gravity wave detectors and in ring-laser gyroscopes. In this paper we analyze
the quantum noise associated with anomalously dispersive cavity modes. The
vacuum field energy associated with a particular cavity mode is proportional to
the cavity-averaged group velocity of that mode. For anomalously dispersive
cavities with group index values between 1 and 0, this means that the total
vacuum field energy associated with a particular cavity mode must exceed . For white light cavities in particular, the group index approaches
zero and the vacuum field energy of a particular spatial mode may be
significantly enhanced. We predict enhanced spontaneous emission rates into
anomalously dispersive cavity modes and broadened laser linewidths when the
linewidth of intracavity emitters is broader than the cavity linewidth.Comment: 9 pages, 4 figure
Wilson-'t Hooft operators in four-dimensional gauge theories and S-duality
We study operators in four-dimensional gauge theories which are localized on
a straight line, create electric and magnetic flux, and in the UV limit break
the conformal invariance in the minimal possible way. We call them Wilson-'t
Hooft operators, since in the purely electric case they reduce to the
well-known Wilson loops, while in general they may carry 't Hooft magnetic
flux. We show that to any such operator one can associate a maximally symmetric
boundary condition for gauge fields on AdS^2\times S^2. We show that Wilson-'t
Hooft operators are classifed by a pair of weights (electric and magnetic) for
the gauge group and its magnetic dual, modulo the action of the Weyl group. If
the magnetic weight does not belong to the coroot lattice of the gauge group,
the corresponding operator is topologically nontrivial (carries nonvanishing 't
Hooft magnetic flux). We explain how the spectrum of Wilson-'t Hooft operators
transforms under the shift of the theta-angle by 2\pi. We show that, depending
on the gauge group, either SL(2,Z) or one of its congruence subgroups acts in a
natural way on the set of Wilson-'t Hooft operators. This can be regarded as
evidence for the S-duality of N=4 super-Yang-Mills theory. We also compute the
one-point function of the stress-energy tensor in the presence of a Wilson-'t
Hooft operator at weak coupling.Comment: 32 pages, latex. v2: references added. v3: numerical factors
corrected, other minor change
On interference among moving sensors and related problems
We show that for any set of points moving along "simple" trajectories
(i.e., each coordinate is described with a polynomial of bounded degree) in
and any parameter , one can select a fixed non-empty
subset of the points of size , such that the Voronoi diagram of
this subset is "balanced" at any given time (i.e., it contains points
per cell). We also show that the bound is near optimal even for
the one dimensional case in which points move linearly in time. As
applications, we show that one can assign communication radii to the sensors of
a network of moving sensors so that at any given time their interference is
. We also show some results in kinetic approximate range
counting and kinetic discrepancy. In order to obtain these results, we extend
well-known results from -net theory to kinetic environments
The Ammann-Beenker tilings revisited
This paper introduces two tiles whose tilings form a one-parameter family of
tilings which can all be seen as digitization of two-dimensional planes in the
four-dimensional Euclidean space. This family contains the Ammann-Beenker
tilings as the solution of a simple optimization problem.Comment: 7 pages, 4 figure
Drived diffusion of vector fields
A model for the diffusion of vector fields driven by external forces is
proposed. Using the renormalization group and the -expansion, the
dynamical critical properties of the model with gaussian noise for dimensions
below the critical dimension are investigated and new transport universality
classes are obtained.Comment: 11 pages, title changed, anisotropic diffusion further discussed and
emphasize
Science with the World Space Observatory - Ultraviolet
The World Space Observatory-Ultraviolet (WSO-UV) will provide access to the
UV range during the next decade. The instrumentation on board will allow to
carry out high resolution imaging, high sensitivity imaging, high resolution
(R~55000) spectroscopy and low resolution (R~2500) long slit spectroscopy. In
this contribution, we briefly outline some of the key science issues that
WSO-UV will address during its lifetime. Among them, of special interest are:
the study of galaxy formation and the intergalactic medium; the astronomical
engines; the Milky Way formation and evol ution, and the formation of the Solar
System and the atmospheres of extrasolar p lanets.Comment: Just one text file (aigomezdecastro.tex). To be published in the
proceeding of the conference: "New Quest in Stellar Astrophysics II: UV
properties of evolved stellar populations" held in Puerto Vallarta - Mexico,
in april 200
Lagrangian Statistics of Dark Halos in a LCDM Cosmology
New statistical properties of dark matter halos in Lagrangian space are
presented. Tracing back the dark matter particles constituting bound halos
resolved in a series of N-body simulations, we measure quantitatively the
correlations of the proto-halo's inertia tensors with the local tidal tensors
and investigate how the correlation strength depends on the proto-halo's
sphericity, local density and filtering scale. It is shown that the majority of
the proto-halos exhibit strong correlations between the two tensors provided
that the tidal field is smoothed on the proto-halo's mass scale. The
correlation strength is found to increase as the proto-halo's sphericity
increases, as the proto-halo's mass increases, and as the local density becomes
close to the critical value, delta_{ec}. It is also found that those peculiar
proto-halos which exhibit exceptionally weak correlations between the two
tensors tend to acquire higher specific angular momentum in Eulerian space,
which is consistent with the linear tidal torque theory. In the light of our
results, it is intriguing to speculate a hypothesis that the low surface
brightness galaxies observed at present epoch correspond to the peculiar
proto-halos with extreme low-sphericity whose inertia tensors are weakly
correlated with the local tidal tensors.Comment: ApJ in press, accepted version, 20 pages, 8 figures, discussion on
LSBGs improved, particle distribution of dark halos in Lagrangian space show
Equilibrium and Dynamical Evolution of Self-Gravitating System Embedded in a Potential Well
Isothermal and self-gravitating systems bound by non-conducting and
conducting walls are known to be unstable if the density contrast between the
center and the boundary exceeds critical values. We investigate the equilibrium
and dynamical evolution of isothermal and self-gravitating system embedded in
potential well, which can be the situation of many astrophysical objects such
as the central parts of the galaxies, or clusters of galaxies with potential
dominated by dark matter, but is still limited to the case where the potential
well is fixed during the evolution. As the ratio between the depth of
surrounding potential well and potential of embedded system becomes large, the
potential well becomes effectively the same boundary condition as conducting
wall, which behaves like a thermal heat bath. We also use the direct N-body
simulation code, NBODY6 to simulate the dynamical evolution of stellar system
embedded in potential wells and propose the equilibrium models for this system.
In deep potential well, which is analogous to the heat bath with high
temperature, the embedded self-gravitating system is dynamically hot, and
loosely bound or can be unbound since the kinetic energy increases due to the
heating by the potential well. On the other hand, the system undergoes core
collapse by self-gravity when potential well is shallow. Binary heating can
stop the collapse and leads to the expansion, but the evolution is very slow
because the potential as a heat bath can absorb the energy generated by the
binaries. The system can be regarded as quasi-static. Density and velocity
dispersion profiles from the N-body simulations in the final quasi-equilibrium
state are similar to our equilibrium models assumed to be in thermal
equilibrium with the potential well.Comment: 12 pages, 12 figures, Submitted to MNRA
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