6,137 research outputs found
On the spectrum of the periodic Dirac operator
The absolute continuity of the spectrum for the periodic Dirac operator is proved given that either , 2q > n-2, or the Fourier series of the
vector potential is absolutely convergent. Here, are continuous matrix functions and \hat V^{(s)}\hat
\alpha_j=(-1}^s\hat \alpha_j\hat V^{(s)} for all anticommuting Hermitian
matrices , , s=0,1.Comment: 17 page
Remarks on a normal subgroup of GA_n
We show that the subgroup generated by locally finite polynomial
automorphisms of k^n is normal in GA_n. Also, some properties of normal
subgroups of GA_n containing all diagonal automorphisms are given.Comment: 5 page
Circular photon drag effect in bulk tellurium
The circular photon drag effect is observed in a bulk semiconductor. The
photocurrent caused by a transfer of both translational and angular momenta of
light to charge carriers is detected in tellurium in the mid-infrared frequency
range. Dependencies of the photocurrent on the light polarization and on the
incidence angle agree with the symmetry analysis of the circular photon drag
effect. Microscopic models of the effect are developed for both intra- and
inter-subband optical absorption in the valence band of tellurium. The shift
contribution to the circular photon drag current is calculated. An observed
decrease of the circular photon drag current with increase of the photon energy
is explained by the theory for inter-subband optical transitions. Theoretical
estimates of the circular photon drag current agree with the experimental data.Comment: 8 pages, 4 figure
Radio-frequency Bloch-transistor electrometer
A quantum-limited electrometer based on charge modulation of the Josephson
supercurrent in the Bloch transistor inserted into a superconducting ring is
proposed. As this ring is inductive coupled to a high-Q resonance tank circuit,
the variations of the charge on the transistor island (input signal) are
converted into variations of amplitude and phase of radio-frequency
oscillations in the tank. These variations are amplified and then detected. The
output noise, the back-action fluctuations and their cross-correlation are
computed. It is shown that our device enables measurements of the charge with a
sensitivity which is determined by the energy resolution of its amplifier, that
can be reduced down to the standard quantum limit of \hbar/2. On the basis of
this setup a "back-action-evading" scheme of the charge measurements is
proposed.Comment: 5 pages incl. 2 figure
Differential Form of the Skornyakov--Ter-Martirosyan Equations
The Skornyakov--Ter-Martirosyan three-boson integral equations in momentum
space are transformed into differential equations. This allows us to take into
account quite directly the Danilov condition providing self-adjointness of the
underlying three-body Hamiltonian with zero-range pair interactions. For the
helium trimer the numerical solutions of the resulting differential equations
are compared with those of the Faddeev-type AGS equations.Comment: 4 pages, 2 figure
Effects of quasiparticle tunneling in a circuit-QED realization of a strongly driven two-level system
We experimentally and theoretically study the frequency shift of a driven
cavity coupled to a superconducting charge qubit. In addition to previous
studies, we here also consider drive strengths large enough to energetically
allow for quasiparticle creation. Quasiparticle tunneling leads to the
inclusion of more than two charge states in the dynamics. To explain the
observed effects, we develop a master equation for the microwave dressed charge
states, including quasiparticle tunneling. A bimodal behavior of the frequency
shift as a function of gate voltage can be used for sensitive charge detection.
However, at weak drives the charge sensitivity is significantly reduced by
non-equilibrium quasiparticles, which induce transitions to a non-sensitive
state. Unexpectedly, at high enough drives, quasiparticle tunneling enables a
very fast relaxation channel to the sensitive state. In this regime, the charge
sensitivity is thus robust against externally injected quasiparticles and the
desired dynamics prevail over a broad range of temperatures. We find very good
agreement between theory and experiment over a wide range of drive strengths
and temperatures.Comment: 25 pages, 7 figure
Global in Time Solutions to Kolmogorov-Feller Pseudodifferential Equations with Small Parameter
The goal in this paper is to demonstrate a new method for constructing
global-in-time approximate (asymptotic) solutions of (pseudodifferential)
parabolic equations with a small parameter. We show that, in the leading term,
such a solution can be constructed by using characteristics, more precisely, by
using solutions of the corresponding Hamiltonian system and without using any
integral representation. For completeness, we also briefly describe the
well-known scheme developed by V.P.Maslov for constructing global-in-time
solutions.Comment: 27 page
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