Generalized Gravitational Entropy from Total Derivative Action

We investigate the generalized gravitational entropy from total derivative terms in the gravitational action. Following the method of Lewkowycz and Maldacena, we find that the generalized gravitational entropy from total derivatives vanishes. We compare our results with the work of Astaneh, Patrushev, and Solodukhin. We find that if total derivatives produced nonzero entropy, the holographic and the field-theoretic universal terms of entanglement entropy would not match. Furthermore, the second law of thermodynamics could be violated if the entropy of total derivatives did not vanish.Comment: 24 pages; v2: added references, Sec. 5.2 for corner entanglement, a toy model in Sec. 5.3, and minor corrections; v3: added one reference, published versio

O(αsv2)O(\alpha_s v^2) correction to e+e−→J/ψ+ηce^+e^-\to J/\psi+\eta_c at BB factories

We investigate the ${\mathcal O}(\alpha_s v^2)$ correction to the $e^+e^-\to J/\psi+\eta_c$ process in the nonrelativistic QCD (NRQCD) factorization approach. Within some reasonable choices of the relative order-$v^2$ NRQCD matrix elements, we find that including this new ingredient of correction only mildly enhances the existing NRQCD predictions. We have also deduced the asymptotic expressions for the ${\mathcal O}(\alpha_s v^2)$ short-distance coefficients, and reconfirm the early speculation that at next-to-leading order in $\alpha_s$, the double logarithm of type $\ln^2 (s/m_c^2)$ appearing in various NRQCD short-distance coefficients is always associated with the helicity-suppressed channels.Comment: v3, 6 pages, 2 figures, 1 table; matching the published versio

Some recent progress in understanding exclusive double charmonium production at BB factories

We review some recent progress in understanding various exclusive double charmonium production processes at $B$ factories, within the nonrelativistic QCD factorization framework. First we investigate the impact of the joint perturbative and relativistic correction on the process that has attracted a great amount of attention in the past decade, $e^+e^-\to J/\psi+\eta_c$. We then briefly discuss the phenomenological implication of the next-to-leading order perturbative correction to the processes $e^+e^-\to J/\psi+\chi_{c0,1,2} (\eta_{c2})$. We further emphasize a novel theoretical challenge, which is recently discovered by applying the NRQCD factorization approach to the helicity-suppressed hard exclusive reactions involving heavy quarkonium.Comment: 9 pages, 2 figures, 1 table. Talk given by Y. J. at the Xth Quark Confinement and the Hadron Spectrum, 8-12 October 2012, TUM Campus Garching, Munich, German

Holographic RG flows with nematic IR phases

We construct zero-temperature geometries that interpolate between a Lifshitz fixed point in the UV and an IR phase that breaks spatial rotations but preserves translations. We work with a simple holographic model describing two massive gauge fields coupled to gravity and a neutral scalar. Our construction can be used to describe RG flows in non-relativistic, strongly coupled quantum systems with nematic order in the IR. In particular, when the dynamical critical exponent of the UV fixed point is z=2 and the IR scaling exponents are chosen appropriately, our model realizes holographically the scaling properties of the bosonic modes of the quadratic band crossing model.Comment: 19 pages, 2 figures. References added. Expanded discussion on nematic orde

The Laplacian Eigenvalues and Invariants of Graphs

In this paper, we investigate some relations between the invariants (including vertex and edge connectivity and forwarding indices) of a graph and its Laplacian eigenvalues. In addition, we present a sufficient condition for the existence of Hamiltonicity in a graph involving its Laplacian eigenvalues.Comment: 10 pages,Filomat, 201