2,602 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
Could the 21-cm absorption be explained by the dark matter suggested by Be transitions?
The stronger than expected 21-cm absorption was observed by EDGES recently,
and another anomaly of Be transitions would be signatures of new
interactions. These two issues may be related to each other, e.g., pseudoscalar
mediated fermionic millicharged dark matter (DM), and the 21-cm absorption
could be induced by photon mediated scattering between MeV millicharged DM and
hydrogen. This will be explored in this paper. For fermionic millicharged DM
with masses in a range of , the
p-wave annihilation would be dominant during DM
freeze-out. The s-wave annihilation is tolerant by constraints from CMB and the 21-cm absorption. The
millicharged DM can evade constraints from direct detection experiments. The
process of with the invisible decay could be employed to search for the millicharged DM, and future high
intensity sources, such as NA62, will do the job.Comment: 6 pages, 2 figures, the accepted version, EPJ
Maximal violation of Clauser-Horne-Shimony-Holt inequality for two qutrits
Bell-Clauser-Horne-Shimony-Holt inequality (in terms of correlation
functions) of two qutrits is studied in detail by employing tritter
measurements. A uniform formula for the maximum value of this inequality for
tritter measurements is obtained. Based on this formula, we show that
non-maximally entangled states violate the Bell-CHSH inequality more strongly
than the maximally entangled one. This result is consistent with what was
obtained by Ac{\'{i}}n {\it et al} [Phys. Rev. A {\bf 65}, 052325 (2002)] using
the Bell-Clauser-Horne inequality (in terms of probabilities).Comment: 6 pages, 3 figure
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