5,234 research outputs found
Collapse of the wavefunction, the information paradox and backreaction
We consider the black hole information problem within the context of collapse
theories in a scheme that allows the incorporation of the backreaction to the
Hawking radiation. We explore the issue in a setting of the two dimensional
version of black hole evaporation known as the Russo-Susskind-Thorlacius model.
We summarize the general ideas based on the semiclassical version of Einstein's
equations and then discuss specific modifications that are required in the
context of collapse theories when applied to this model.Comment: 44 pages, 4 figure
Spin injection into a metal from a topological insulator
We study a junction of a topological insulator with a thin two-dimensional
(2D) non-magnetic or partially polarized ferromagnetic metallic film deposited
on a 3D insulator. We show that such a junction leads to a finite spin current
injection into the film whose magnitude can be controlled by tuning a voltage
applied across the junction. For ferromagnetic films, the direction of the
component of the spin current along the film magnetization can also be tuned by
tuning the barrier potential at the junction. We point out the role of
the chiral spin-momentum locking of the Dirac electrons behind this phenomenon
and suggest experiments to test our theory.Comment: Revised version with supplemental material
Tracking down localized modes in PT-symmetric Hamiltonians under the influence of a competing nonlinearity
The relevance of parity and time reversal (PT)-symmetric structures in
optical systems is known for sometime with the correspondence existing between
the Schrodinger equation and the paraxial equation of diffraction where the
time parameter represents the propagating distance and the refractive index
acts as the complex potential. In this paper, we systematically analyze a
normalized form of the nonlinear Schrodinger system with two new families of
PT-symmetric potentials in the presence of competing nonlinearities. We
generate a class of localized eigenmodes and carry out a linear stability
analysis on the solutions. In particular, we find an interesting feature of
bifurcation charaterized by the parameter of perturbative growth rate passing
through zero where a transition to imaginary eigenvalues occurs.Comment: 10pages, To be published in Acta Polytechnic
Fermionic Chern-Simons Theory of SU(4) Fractional Quantum Hall Effect
We develop a Fermionic Chern-Simons (CS) theory for the fractional quantum
Hall effect in monolayer graphene with SU(4) symmetry, arising from the spin
and the valley degrees of freedom, which involves four distinct CS gauge
fields. We choose the corresponding elements of the CS coupling matrix such
that an even number of spin and valley quantum number dependent flux quanta is
attached to all electrons and that any electron with a given spin and valley
quantum number sees an integer number of flux attached to other electrons with
different (spin and valley) quantum numbers. Using this CS matrix, we obtain a
list of possible fractional quantum Hall states that might occur in graphene
and propose wavefunctions for those states. Our analysis also applies to
fractional quantum Hall states of both bilayer quantum Hall systems without
spin polarization and bilayer spin polarized graphene.Comment: v1; 1 Fig, 2 Tables, 7+ page
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