2,220 research outputs found
Transient tunneling effects of resonance doublets in triple barrier systems
Transient tunneling effects in triple barrier systems are investigated by
considering a time-dependent solution to the Schr\"{o}dinger equation with a
cutoff wave initial condition. We derive a two-level formula for incidence
energies near the first resonance doublet of the system. Based on that
expression we find that the probability density along the internal region of
the potential, is governed by three oscillation frequencies: one of them refers
to the well known Bohr frequency, given in terms of the first and second
resonance energies of the doublet, and the two others, represent a coupling
with the incidence energy . This allows to manipulate the above frequencies
to control the tunneling transient behavior of the probability density in the
short-time regim
Rare top decay and CP violation in THDM
We discuss the formalism of two Higgs doublet model type III with CP
violation from CP-even CP-odd mixing in the neutral Higgs bosons. The flavor
changing interactions among neutral Higgs bosons and fermions are presented at
tree level in this type of model. These assumptions allow the study rare top
decays mediated by neutral Higgs bosons, particularly we are interested in
. For this process we estimated upper bounds of the
branching ratios of the order of
for a neutral Higgs boson mass of 125 GeV and
, 1.5, 2, 2.5. For the case of the
number of possible events is estimated from 1 to 10 events which could be
observed in future experiments at LHC with a luminosity of 300
and 14 GeV for the energy of the center of mass. Also we
estimate that the number of events for the process in
different scenarios is of order of .Comment: 8 pages, 5 figure
Nonabelian 2D Gauge Theories for Determinantal Calabi-Yau Varieties
The two-dimensional supersymmetric gauged linear sigma model (GLSM) with
abelian gauge groups and matter fields has provided many insights into string
theory on Calabi--Yau manifolds of a certain type: complete intersections in
toric varieties. In this paper, we consider two GLSM constructions with
nonabelian gauge groups and charged matter whose infrared CFTs correspond to
string propagation on determinantal Calabi-Yau varieties, furnishing another
broad class of Calabi-Yau geometries in addition to complete intersections. We
show that these two models -- which we refer to as the PAX and the PAXY model
-- are dual descriptions of the same low-energy physics. Using GLSM techniques,
we determine the quantum K\"ahler moduli space of these varieties and find no
disagreement with existing results in the literature.Comment: v3: 46 pages, 1 figure. Corrected phase structure of general linear
determinantal varieties. Typos correcte
Two-Sphere Partition Functions and Gromov-Witten Invariants
Many N=(2,2) two-dimensional nonlinear sigma models with Calabi-Yau target
spaces admit ultraviolet descriptions as N=(2,2) gauge theories (gauged linear
sigma models). We conjecture that the two-sphere partition function of such
ultraviolet gauge theories -- recently computed via localization by Benini et
al. and Doroud et al. -- yields the exact K\"ahler potential on the quantum
K\"ahler moduli space for Calabi-Yau threefold target spaces. In particular,
this allows one to compute the genus zero Gromov-Witten invariants for any such
Calabi-Yau threefold without the use of mirror symmetry. More generally, when
the infrared superconformal fixed point is used to compactify string theory,
this provides a direct method to compute the spacetime K\"ahler potential of
certain moduli (e.g., vector multiplet moduli in type IIA), exactly in
{\alpha}'. We compute these quantities for the quintic and for R{\o}dland's
Pfaffian Calabi-Yau threefold and find agreement with existing results in the
literature. We then apply our methods to a codimension four determinantal
Calabi-Yau threefold in P^7, recently given a nonabelian gauge theory
description by the present authors, for which no mirror Calabi-Yau is currently
known. We derive predictions for its Gromov-Witten invariants and verify that
our predictions satisfy nontrivial geometric checks.Comment: 25 pages + 2 appendices; v2 corrects a divisor in K\"ahler moduli
space and includes a new calculation that confirms a geometric prediction; v3
contains minor update of Gromov-Witten invariant extraction procedur
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