2,872 research outputs found
Defect and Hodge numbers of hypersurfaces
We define defect for hypersurfaces with A-D-E singularities in complex
projective normal Cohen-Macaulay fourfolds having some vanishing properties of
Bott-type and prove formulae for Hodge numbers of big resolutions of such
hypersurfaces. We compute Hodge numbers of Calabi-Yau manifolds obtained as
small resolutions of cuspidal triple sextics and double octics with higher A_j
singularities.Comment: 25 page
Quartic double solids with ordinary singularities
We study the mixed Hodge structure on the third homology group of a threefold
which is the double cover of projective three-space ramified over a quartic
surface with a double conic. We deal with the Torelli problem for such
threefolds.Comment: 14 pages, presented at the Conference Arnol'd 7
Elliptic curve configurations on Fano surfaces
The elliptic curves on a surface of general type constitute an obstruction
for the cotangent sheaf to be ample. In this paper, we give the classification
of the configurations of the elliptic curves on the Fano surface of a smooth
cubic threefold. That means that we give the number of such curves, their
intersections and a plane model. This classification is linked to the
classification of the automorphism groups of theses surfaces.Comment: 17 pages, accepted and shortened version, the rest will appear in
"Fano surfaces with 12 or 30 elliptic curves
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
Brown Dwarfs and the Cataclysmic Variable Period Minimum
Using improved, up-to-date stellar input physics tested against observations
of low-mass stars and brown dwarfs we calculate the secular evolution of
low-mass donor cataclysmic variables (CVs), including those which form with a
brown dwarf donor. Our models confirm the mismatch between the calculated
minimum period (Pmin ~ 70 min) and the observed short-period cut-off (~ 80 min)
in the CV period histogram. We find that tidal and rotational corrections
applied to the one-dimensional stellar structure equations have no significant
effect on the period minimum. Theoretical period distributions synthesized from
our model sequences always show an accumulation of systems at the minimum
period, a feature absent from the observed distribution. We suggest that
non-magnetic CVs become unobservable as they are effectively trapped in
permanent quiescence before they reach Pmin, and that small-number statistics
may hide the period spike for magnetic CVs.Comment: 10 pages; accepted for publication in MNRA
Non-birational twisted derived equivalences in abelian GLSMs
In this paper we discuss some examples of abelian gauged linear sigma models
realizing twisted derived equivalences between non-birational spaces, and
realizing geometries in novel fashions. Examples of gauged linear sigma models
with non-birational Kahler phases are a relatively new phenomenon. Most of our
examples involve gauged linear sigma models for complete intersections of
quadric hypersurfaces, though we also discuss some more general cases and their
interpretation. We also propose a more general understanding of the
relationship between Kahler phases of gauged linear sigma models, namely that
they are related by (and realize) Kuznetsov's `homological projective duality.'
Along the way, we shall see how `noncommutative spaces' (in Kontsevich's sense)
are realized physically in gauged linear sigma models, providing examples of
new types of conformal field theories. Throughout, the physical realization of
stacks plays a key role in interpreting physical structures appearing in GLSMs,
and we find that stacks are implicitly much more common in GLSMs than
previously realized.Comment: 54 pages, LaTeX; v2: typo fixe
Validity of the Independent-Particle Approximation in X-Ray Photoemission: The Exception, Not the Rule
A combined experimental and theoretical study of argon valence photoionization illustrates the discovery of the broad lack of validity of the independent-particle approximation (IPA) for x-ray photoemission. In addition to previously known breakdowns of the IPA, which are limited to high photon energies and regions very near threshold, the observed breakdown in photoionization at intermediate energies demonstrates generally that the IPA is valid only in very restricted domains. These restrictions are expected to be relevant throughout the periodic table, with consequences for a wide variety of applications
High flux cold Rubidium atomic beam for strongly coupled Cavity QED
This paper presents a setup capable of producing a high-flux continuous beam
of cold rubidium atoms for cavity QED experiments in the regime of strong
coupling. A 2 MOT, loaded by rubidium getters in a dry film coated vapor
cell, fed a secondary moving-molasses MOT (MM-MOT) at a rate of 1.5 x
atoms/sec. The MM-MOT provided a continuous beam with tunable velocity. This
beam was then directed through the waist of a 280 m cavity resulting in a
Rabi splitting of more than +/- 10 MHz. The presence of sufficient number of
atoms in the cavity mode also enabled splitting in the polarization
perpendicular to the input. The cavity was in the strong coupling regime, with
parameters (g, , )/2 equal to (7, 3, 6)/ 2 MHz.Comment: Journal pape
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