52 research outputs found
Lagrangian Floer superpotentials and crepant resolutions for toric orbifolds
We investigate the relationship between the Lagrangian Floer superpotentials
for a toric orbifold and its toric crepant resolutions. More specifically, we
study an open string version of the crepant resolution conjecture (CRC) which
states that the Lagrangian Floer superpotential of a Gorenstein toric orbifold
and that of its toric crepant resolution coincide after
analytic continuation of quantum parameters and a change of variables. Relating
this conjecture with the closed CRC, we find that the change of variable
formula which appears in closed CRC can be explained by relations between open
(orbifold) Gromov-Witten invariants. We also discover a geometric explanation
(in terms of virtual counting of stable orbi-discs) for the specialization of
quantum parameters to roots of unity which appears in Y. Ruan's original CRC
["The cohomology ring of crepant resolutions of orbifolds", Gromov-Witten
theory of spin curves and orbifolds, 117-126, Contemp. Math., 403, Amer. Math.
Soc., Providence, RI, 2006]. We prove the open CRC for the weighted projective
spaces using an equality between open
and closed orbifold Gromov-Witten invariants. Along the way, we also prove an
open mirror theorem for these toric orbifolds.Comment: 48 pages, 1 figure; v2: references added and updated, final version,
to appear in CM
Conductance oscillations of a spin-orbit stripe with polarized contacts
We investigate the linear conductance of a stripe of spin-orbit interaction
in a 2D electron gas; that is, a 2D region of length along the transport
direction and infinite in the transverse one in which a spin-orbit interaction
of Rashba type is present. Polarization in the contacts is described by means
of Zeeman fields. Our model predicts two types of conductance oscillations:
Ramsauer oscillations in the minority spin transmission, when both spins can
propagate, and Fano oscillations when only one spin propagates. The latter are
due to the spin-orbit coupling with quasibound states of the non propagating
spin. In the case of polarized contacts in antiparallel configuration Fano-like
oscillations of the conductance are still made possible by the spin orbit
coupling, even though no spin component is bound by the contacts. To describe
these behaviors we propose a simplified model based on an ansatz wave function.
In general, we find that the contribution for vanishing transverse momentum
dominates and defines the conductance oscillations. Regarding the oscillations
with Rashba coupling intensity, our model confirms the spin transistor
behavior, but only for high degrees of polarization. Including a position
dependent effective mass yields additional oscillations due to the mass jumps
at the interfaces.Comment: 8.5 pages, 9 figure
Desenvolvimento e avaliação de dispositivos de controle de vazão derivada em canais de irrigação.
bitstream/CNPMS/18885/1/Doc_44.pd
WIATEC: A World Integrated Assessment Model of Global Trade Environment and Climate Change
Polaron and bipolaron formation in the Hubbard-Holstein model: role of next-nearest neighbor electron hopping
The influence of next-nearest neighbor electron hopping, , on the
polaron and bipolaron formation in a square Hubbard-Holstein model is
investigated within a variational approach. The results for electron-phonon and
electron-electron correlation functions show that a negative value of
induces a strong anisotropy in the lattice distortions favoring
the formation of nearest neighbor intersite bipolaron. The role of
, electron-phonon and electron-electron interactions is briefly
discussed in view of the formation of charged striped domains.Comment: 4 figure
Froehlich Polaron and Bipolaron: Recent Developments
It is remarkable how the Froehlich polaron, one of the simplest examples of a
Quantum Field Theoretical problem, as it basically consists of a single fermion
interacting with a scalar Bose field of ion displacements, has resisted full
analytical or numerical solution at all coupling since 1950, when its
Hamiltonian was first written. The field has been a testing ground for
analytical, semi-analytical, and numerical techniques, such as path integrals,
strong-coupling perturbation expansion, advanced variational, exact
diagonalisation (ED), and quantum Monte Carlo (QMC) techniques. This article
reviews recent developments in the field of continuum and discrete (lattice)
Froehlich (bi)polarons starting with the basics and covering a number of active
directions of research.Comment: 131 pages, 17 figures, 409 references, appear in Reports on Progress
in Physic
Lopinavir/ritonavir and darunavir/cobicistat in hospitalized covid-19 patients: Findings from the multicenter italian corist study
- …