1,082 research outputs found
Topological Strings and Quantum Spectral Problems
We consider certain quantum spectral problems appearing in the study of local
Calabi-Yau geometries. The quantum spectrum can be computed by the
Bohr-Sommerfeld quantization condition for a period integral. For the case of
small Planck constant, the periods are computed perturbatively by deformation
of the Omega background parameters in the Nekrasov-Shatashvili limit. We
compare the calculations with the results from the standard perturbation theory
for the quantum Hamiltonian. There have been proposals in the literature for
the non-perturbative contributions based on singularity cancellation with the
perturbative contributions. We compute the quantum spectrum numerically with
some high precisions for many cases of Planck constant. We find that there are
also some higher order non-singular non-perturbative contributions, which are
not captured by the singularity cancellation mechanism. We fix the first few
orders formulas of such corrections for some well known local Calabi-Yau
models.Comment: 47 pages, 3 figures. v2: journal version, typos correcte
Giant negative magnetoresistance induced by the chiral anomaly in individual Cd3As2 nanowires
Cd3As2 is a newly booming Dirac semimetal with linear dispersion along all
three momentum directions and can be viewed as 3D analog of graphene. As
breaking of either time reversal symmetry or spatial inversion symmetry, the
Dirac semimetal is believed to transform into Weyl semimetal with exotic chiral
anomaly effect, while the experimental evidence of the chiral anomaly is still
missing in Cd3As2. Here we report the magneto-transport properties of
individual Cd3As2 nanowires. Large negative magnetoresistance (MR) with
magnitude of -63% at 60 K and -11% at 300 K are observed when the magnetic
field is parallel with the electric field direction, giving the evidence of the
chiral magnetic effect in Cd3As2 nanowires. In addition, the critical magnetic
field BC, where there is an extremum of the negative MR, increases with
increasing temperature. As the first observation of chiral anomaly induced
negative MR in Cd3As2 nanowires, it may offer valuable insights for low
dimensional physics in Dirac semimetals.Comment: 4 figure
Iterative Schemes by a New Generalized Resolvent for a Monotone Mapping and a Relatively Weak Nonexpansive Mapping
We introduce a new generalized resolvent in a Banach space and discuss some of its properties. Using these properties, we obtain an iterative scheme for finding a point which is a fixed point of relatively weak nonexpansive mapping and a zero of monotone mapping. Furthermore, strong convergence of the scheme to a point which is a fixed point of relatively weak nonexpansive mapping and a zero of monotone mapping is proved
Ballistic Thermal Rectification in Asymmetric Three-Terminal Mesoscopic Dielectric Systems
By coupling the asymmetric three-terminal mesoscopic dielectric system with a
temperature probe, at low temperature, the ballistic heat flux flow through the
other two asymmetric terminals in the nonlinear response regime is studied
based on the Landauer formulation of transport theory. The thermal
rectification is attained at the quantum regime. It is a purely quantum effect
and is determined by the dependence of the ratio
on , the phonon's frequency.
Where and are respectively the
transmission coefficients from two asymmetric terminals to the temperature
probe, which are determined by the inelastic scattering of ballistic phonons in
the temperature probe. Our results are confirmed by extensive numerical
simulations.Comment: 10 pages, 4 figure
Varstrometry Selected Radio-Loud Candidates of Dual and Off-Nucleus Quasars at Sub-kpc Scales
Dual super massive black holes at sub-kpc to kpc scales, the product of
galaxy mergers, are progenitors of eventually coalescing binary SMBHs. If both
or one of the dual SMBHs are accreting, they may appear as dual AGNs or
off-nucleus AGNs. Studying such systems is essential to learn the dynamical
evolution of binary SMBHs as well as the process of galaxy merging. Recently a
novel astrometry-based method named varstrometry has been put forward to search
for dual SMBHs at high redshift, as the unsynchronized flux variability of dual
AGNs (or off-nucleus AGNs) will cause astrometric jitters detectable by Gaia
without spatially resolving them. Based on Gaia varstrometry we select a rare
sample of 5 radio loud quasars with clear Gaia astrometric jitters. With
e-MERLIN observations we have revealed a single compact radio source for each
of them. Remarkably all but one exhibit clear Gaia-radio offsets of ~ 9 -- 60
mas. The observed Gaia jitters appear consistent with the expected values.
These detected Gaia-radio offsets suggest these candidate dual SMBHs may have
projected separations as small as ~ 0.01 -- 0.1'' (~ 0.1 kpc, depending on the
optical flux ratio of two SMBHs). Meanwhile, this work highlights the
remarkably high efficiency of Gaia varstrometry selection of jittering sources.Comment: 6 pages, 5 figures, 1 table; accepted for publication in MNRAS
Letter
- …