A stroboscopic averaging algorithm for highly oscillatory delay problems

We propose and analyze a heterogenous multiscale method for the efficient integration of constant-delay differential equations subject to fast periodic forcing. The stroboscopic averaging method (SAM) suggested here may provide approximations with \(\mathcal{O}(H^2+1/\Omega^2)\) errors with a computational effort that grows like \(H^{-1}\) (the inverse of the stepsize), uniformly in the forcing frequency Omega

Learning distance to subspace for the nearest subspace methods in high-dimensional data classification

The nearest subspace methods (NSM) are a category of classification methods widely applied to classify high-dimensional data. In this paper, we propose to improve the classification performance of NSM through learning tailored distance metrics from samples to class subspaces. The learned distance metric is termed as ‘learned distance to subspace’ (LD2S). Using LD2S in the classification rule of NSM can make the samples closer to their correct class subspaces while farther away from their wrong class subspaces. In this way, the classification task becomes easier and the classification performance of NSM can be improved. The superior classification performance of using LD2S for NSM is demonstrated on three real-world high-dimensional spectral datasets

Octet Baryon Charge Radii, Chiral Symmetry and Decuplet Intermediate States

We compute the octet baryon charge radii to O(1/Heavy^3) in heavy baryon chiral perturbation theory. We examine the effect of including the decuplet of spin-3/2 baryons explicitly. We find that it does no t improve the level of agreement between the HBchiPT and experimental values for the Sigma^- charge radius.Comment: 9 pages, 2 figures. Uses axodraw.sty, include

Phonon-phason coupling in icosahedral quasicrystals

From relaxation simulations of decoration-based quasicrystal structure models using microscopically based interatomic pair potentials, we have calculated the (usually neglected) phonon-phason coupling constant. Its sign is opposite for the two alloys studied, i-AlMn and i-(Al,Cu)Li; a dimensionless measure of its magnitude relative to the phonon and phason elastic constants is of order 1/10, suggesting its effects are small but detectable. We also give a criterion for when phonon-phason effects are noticeable in diffuse tails of Bragg peaks.Comment: 7 pages, LaTeX, uses Europhys Lett macros (included

Nonlinear Schr\"odinger Equation for Superconductors

Using the Hartree-Fock-Bogoliubov factorization of the density matrix and the Born-Oppenheimer approximation we show that the motion of the condensate satisfies a nonlinear Schr\"odinger equation in the zero temperature limit. The Galilean invariance of the equation is explicitly manifested. {}From this equation some general properties of a superconductor, such as Josephson effects, the Magnus force, and the Bogoliubov-Anderson mode can be obtained readily.Comment: Latex, 12 page

Mechanism for current saturation and energy dissipation in graphene transistors

From a combination of careful and detailed theoretical and experimental studies, we demonstrate that the Boltzmann theory including all scattering mechanisms gives an excellent account, with no adjustable parameters, of high electric field transport in single as well as double-oxide graphene transistors. We further show unambiguously that scattering from the substrate and superstrate surface optical (SO) phonons governs the high field transport and heat dissipation over a wide range of experimentally relevant parameters. Models that neglect SO phonons altogether or treat them in a simple phenomenological manner are inadequate. We outline possible strategies for achieving higher current and complete saturation in graphene devices.Comment: revtex, 5 pages, 3 figures, to appear in Phys. Rev. Lett

Is Explicit Congestion Notification usable with UDP?

We present initial measurements to determine if ECN is usable with UDP traffic in the public Internet. This is interesting because ECN is part of current IETF proposals for congestion control of UDPbased interactive multimedia, and due to the increasing use of UDP as a substrate on which new transport protocols can be deployed. Using measurements from the author’s homes, their workplace, and cloud servers in each of the nine EC2 regions worldwide, we test reachability of 2500 servers from the public NTP server pool, using ECT(0) and not-ECT marked UDP packets. We show that an average of 98.97% of the NTP servers that are reachable using not-ECT marked packets are also reachable using ECT(0) marked UDP packets, and that ~98% of network hops pass ECT(0) marked packets without clearing the ECT bits. We compare reachability of the same hosts using ECN with TCP, finding that 82.0% of those reachable with TCP can successfully negotiate and use ECN. Our findings suggest that ECN is broadly usable with UDP traffic, and that support for use of ECN with TCP has increased