207 research outputs found
Photon decay gamma->nu anti-nu in an external magnetic field
The process of the photon decay into the neutrino - antineutrino pair in a
magnetic field is investigated. The amplitude and the probability are analysed
in the limits of relatively small and strong fields. The probability is
suppressed by a factor (G_F m^2_e)^2 as compared with the probability of the
pure electromagnetic process gamma -> e- e+. However, the process with
neutrinos could play a role of an additional channel of stellar energy-loss.Comment: 8 pages, LaTeX, typos fixed, minor modifications, version accepted to
Physics Letters
The symplectic Deligne-Mumford stack associated to a stacky polytope
We discuss a symplectic counterpart of the theory of stacky fans. First, we
define a stacky polytope and construct the symplectic Deligne-Mumford stack
associated to the stacky polytope. Then we establish a relation between stacky
polytopes and stacky fans: the stack associated to a stacky polytope is
equivalent to the stack associated to a stacky fan if the stacky fan
corresponds to the stacky polytope.Comment: 20 pages; v2: To appear in Results in Mathematic
Electromagnetic catalysis of the radiative transitions of type in the field of an intense monochromatic wave
The radiative decay of the massive neutrino
in a circularly polarized electromagnetic wave is investigated within the
Standard theory with lepton mixing. The decay probability in the wave field
does not contain a threshold factor as opposed to the
decay probability in a vacuum or in a constant uniform external field. The
phenomenon of the gigantic enhancement ( ) of the neutrino decay
probability in external wave field is discovered. The probability of the photon
splitting into the neutrino pair is obtained. (Published in Phys.Lett.B 321
(1994) 108).Comment: 10 pages, LaTeX (using emlines2.sty), Yaroslavl, Yaroslavl State
University preprint YARU-HE-93/0
On the Crepant Resolution Conjecture in the Local Case
In this paper we analyze four examples of birational transformations between
local Calabi-Yau 3-folds: two crepant resolutions, a crepant partial
resolution, and a flop. We study the effect of these transformations on
genus-zero Gromov-Witten invariants, proving the
Coates-Corti-Iritani-Tseng/Ruan form of the Crepant Resolution Conjecture in
each case. Our results suggest that this form of the Crepant Resolution
Conjecture may also hold for more general crepant birational transformations.
They also suggest that Ruan's original Crepant Resolution Conjecture should be
modified, by including appropriate "quantum corrections", and that there is no
straightforward generalization of either Ruan's original Conjecture or the
Cohomological Crepant Resolution Conjecture to the case of crepant partial
resolutions. Our methods are based on mirror symmetry for toric orbifolds.Comment: 27 pages. This is a substantially revised and shortened version of my
preprint "Wall-Crossings in Toric Gromov-Witten Theory II: Local Examples";
all results contained here are also proved there. To appear in Communications
in Mathematical Physic
Exceptional collections and D-branes probing toric singularities
We demonstrate that a strongly exceptional collection on a singular toric
surface can be used to derive the gauge theory on a stack of D3-branes probing
the Calabi-Yau singularity caused by the surface shrinking to zero size. A
strongly exceptional collection, i.e., an ordered set of sheaves satisfying
special mapping properties, gives a convenient basis of D-branes. We find such
collections and analyze the gauge theories for weighted projective spaces, and
many of the Y^{p,q} and L^{p,q,r} spaces. In particular, we prove the strong
exceptionality for all p in the Y^{p,p-1} case, and similarly for the
Y^{p,p-2r} case.Comment: 49 pages, 6 figures; v2 refs added; v3 published versio
SUSY vertex algebras and supercurves
This article is a continuation of math.QA/0603633 Given a strongly conformal
SUSY vertex algebra V and a supercurve X we construct a vector bundle V_X on X,
the fiber of which, is isomorphic to V. Moreover, the state-field
correspondence of V canonically gives rise to (local) sections of these vector
bundles. We also define chiral algebras on any supercurve X, and show that the
vector bundle V_X, corresponding to a SUSY vertex algebra, carries the
structure of a chiral algebra.Comment: 50 page
C^2/Z_n Fractional branes and Monodromy
We construct geometric representatives for the C^2/Z_n fractional branes in
terms of branes wrapping certain exceptional cycles of the resolution. In the
process we use large radius and conifold-type monodromies, and also check some
of the orbifold quantum symmetries. We find the explicit Seiberg-duality which
connects our fractional branes to the ones given by the McKay correspondence.
We also comment on the Harvey-Moore BPS algebras.Comment: 34 pages, v1 identical to v2, v3: typos fixed, discussion of
Harvey-Moore BPS algebras update
Deriving the mass of particles from Extended Theories of Gravity in LHC era
We derive a geometrical approach to produce the mass of particles that could
be suitably tested at LHC. Starting from a 5D unification scheme, we show that
all the known interactions could be suitably deduced as an induced symmetry
breaking of the non-unitary GL(4)-group of diffeomorphisms. The deformations
inducing such a breaking act as vector bosons that, depending on the
gravitational mass states, can assume the role of interaction bosons like
gluons, electroweak bosons or photon. The further gravitational degrees of
freedom, emerging from the reduction mechanism in 4D, eliminate the hierarchy
problem since generate a cut-off comparable with electroweak one at TeV scales.
In this "economic" scheme, gravity should induce the other interactions in a
non-perturbative way.Comment: 30 pages, 1 figur
Superstrings on PP-Wave Backgrounds and Symmetric Orbifolds
We study the superstring theory on pp-wave background with NSNS-flux that is
realized as the Penrose limit of AdS_3 x S^3 x M^4, where M^4 is T^4 or
T^4/Z_2(~ K3). Quantizing this system in the covariant gauge, we explicitly
construct the space-time supersymmetry algebra and the complete set of DDF
operators. We analyse the spectrum of physical states by using the spectrally
flowed representations of current algebra. This spectrum is classified by the
``short string sectors'' and the ``long string sectors'' as in AdS_3 string
theory. The states of the latter propagate freely along the transverse plane of
pp-wave background, but the states of the former do not. We compare the short
string spectrum with the BPS and almost BPS states which have large R-charges
in the symmetric orbifold conformal theory, which is known as the candidate of
dual theory of superstrings on AdS_3 x S^3 x M^4. We show that every short
string states can be embedded successfully in the single particle Hilbert space
of symmetric orbifold conformal theory.Comment: Latex, 35 pages, minor change
Search for direct production of charginos and neutralinos in events with three leptons and missing transverse momentum in √s = 7 TeV pp collisions with the ATLAS detector
A search for the direct production of charginos and neutralinos in final states with three electrons or muons and missing transverse momentum is presented. The analysis is based on 4.7 fb−1 of proton–proton collision data delivered by the Large Hadron Collider and recorded with the ATLAS detector. Observations are consistent with Standard Model expectations in three signal regions that are either depleted or enriched in Z-boson decays. Upper limits at 95% confidence level are set in R-parity conserving phenomenological minimal supersymmetric models and in simplified models, significantly extending previous results
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