7,244 research outputs found
On Optimal Weighted-Delay Scheduling in Input-Queued Switches
Motivated by relatively few delay-optimal scheduling results, in comparison
to results on throughput optimality, we investigate an input-queued switch
scheduling problem in which the objective is to minimize a linear function of
the queue-length vector. Theoretical properties of variants of the well-known
MaxWeight scheduling algorithm are established within this context, which
includes showing that these algorithms exhibit optimal heavy-traffic
queue-length scaling. For the case of input-queued switches, we
derive an optimal scheduling policy and establish its theoretical properties,
demonstrating fundamental differences with the variants of MaxWeight
scheduling. Our theoretical results are expected to be of interest more broadly
than input-queued switches. Computational experiments demonstrate and quantify
the benefits of our optimal scheduling policy
Collective modes of a helical liquid
We study low energy collective modes and transport properties of the "helical
metal" on the surface of a topological insulator. At low energies, electrical
transport and spin dynamics at the surface are exactly related by an operator
identity equating the electric current to the in-plane components of the spin
degrees of freedom. From this relation it follows that an undamped spin wave
always accompanies the sound mode in the helical metal -- thus it is possible
to `hear' the sound of spins. In the presence of long range Coulomb
interactions, the surface plasmon mode is also coupled to the spin wave, giving
rise to a hybridized "spin-plasmon" mode. We make quantitative predictions for
the spin-plasmon in , and discuss its detection in a
spin-grating experiment.Comment: 4 Pages, 2 Figure
Heat-evoked activation of TRPV4 channels in an HEK-293 cell expression system and in native mouse aorta endothelial cells
Peer reviewe
Charge and spin collective modes in a quasi-1D model of Sr2RuO4
Given that Sr2RuO4 is a two-component p-wave superconductor, there exists the
possibility of well defined collective modes corresponding to fluctuations of
the relative phase and spin-orientation of the two components of the order
parameter. We demonstrate that at temperatures much below Tc, these modes have
energies small compared to the pairing gap scale if the superconductivity
arises primarily from the quasi 1D (dxz and dyz) bands, while it is known that
their energies become comparable to the pairing gap scale if there is a
substantial involvement of the quasi 2D (dxy) band. Therefore, the orbital
origin of the superconductivity can be determined by measuring the energies of
these collective modes.Comment: 11 pages (6 pages for main text), 2 figure
Majorana zero modes in a quantum Ising chain with longer-ranged interactions
A one-dimensional Ising model in a transverse field can be mapped onto a
system of spinless fermions with p-wave superconductivity. In the weak-coupling
BCS regime, it exhibits a zero energy Majorana mode at each end of the chain.
Here, we consider a variation of the model, which represents a superconductor
with longer ranged kinetic energy and pairing amplitudes, as is likely to occur
in more realistic systems. It possesses a richer zero temperature phase diagram
and has several quantum phase transitions. From an exact solution of the model
these phases can be classified according to the number of Majorana zero modes
of an open chain: 0, 1, or 2 at each end. The model posseses a multicritical
point where phases with 0, 1, and 2 Majorana end modes meet. The number of
Majorana modes at each end of the chain is identical to the topological winding
number of the Anderson's pseudospin vector that describes the BCS Hamiltonian.
The topological classification of the phases requires a unitary time-reversal
symmetry to be present. When this symmetry is broken, only the number of
Majorana end modes modulo 2 can be used to distinguish two phases. In one of
the regimes, the wave functions of the two phase shifted Majorana zero modes
decays exponentially in space but but in an oscillatory manner. The wavelength
of oscillation is identical to the asymptotic connected spin-spin correlation
of the XY-model in a transverse field to which our model is dual.Comment: 11 pages, 8 figures; brief clarifying comments added; few new
references; this version is accepted in Phys. Rev.
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