Particle current in symmetric exclusion process with time-dependent hopping rates

In a recent study, (Jain et al 2007 Phys. Rev. Lett. 99 190601), a symmetric exclusion process with time-dependent hopping rates was introduced. Using simulations and a perturbation theory, it was shown that if the hopping rates at two neighboring sites of a closed ring vary periodically in time and have a relative phase difference, there is a net DC current which decreases inversely with the system size. In this work, we simplify and generalize our earlier treatment. We study a model where hopping rates at all sites vary periodically in time, and show that for certain choices of relative phases, a DC current of order unity can be obtained. Our results are obtained using a perturbation theory in the amplitude of the time-dependent part of the hopping rate. We also present results obtained in a sudden approximation that assumes large modulation frequency.Comment: 17 pages, 2 figure

Edge Magnetoplasmons in Quantum Hall Line Junction Systems

A quantum Hall line junction system consists of a one-dimensional Luttinger liquid (LL) and two chiral channels that allow density waves incident upon and reflected by the LL to be measured separately. We demonstrate that interactions in a quantum Hall line junction system can be probed by studying edge magnetoplasmon absorption spectra and their polarization dependences. Strong interactions in the junction lead to collective modes that are isolated in either Luttinger liquid or contact subsystems.Comment: 4 pages, 3 figures, submitted to Phys. Rev. B Rapid Communicatio

Stochastic pump effect and geometric phases in dissipative and stochastic systems

The success of Berry phases in quantum mechanics stimulated the study of similar phenomena in other areas of physics, including the theory of living cell locomotion and motion of patterns in nonlinear media. More recently, geometric phases have been applied to systems operating in a strongly stochastic environment, such as molecular motors. We discuss such geometric effects in purely classical dissipative stochastic systems and their role in the theory of the stochastic pump effect (SPE).Comment: Review. 35 pages. J. Phys. A: Math, Theor. (in press

Nonequilibrium thermodynamics as a gauge theory

We assume that markovian dynamics on a finite graph enjoys a gauge symmetry under local scalings of the probability density, derive the transformation law for the transition rates and interpret the thermodynamic force as a gauge potential. A widely accepted expression for the total entropy production of a system arises as the simplest gauge-invariant completion of the time derivative of Gibbs's entropy. We show that transition rates can be given a simple physical characterization in terms of locally-detailed-balanced heat reservoirs. It follows that Clausius's measure of irreversibility along a cyclic transformation is a geometric phase. In this picture, the gauge symmetry arises as the arbitrariness in the choice of a prior probability. Thermostatics depends on the information that is disposable to an observer; thermodynamics does not.Comment: 6 pages. Non-fatal errors in eq.(6), eq.(26) and eq.(31) have been amende

Comment on "Exact results for survival probability in the multistate Landau-Zener model"

We correct the proof of Brundobler-Elser formula (BEF) provided in [2004 \textit{J. Phys. B: At. Mol. Opt. Phys.} \textbf{37} 4069] and continued in Appendix of [2005 \textit{J. Phys. B: At. Mol. Opt. Phys.} \textbf{38} 907]. After showing that some changes of variables employed in these articles are used erroneously, we propose an alternative change of variables which solves the problem. In our proof, we reveal the connection between the BEF for a general $N$-level Landau-Zener system and the exactly solvable bow-tie model. The special importance of the diabatic levels with maximum/minimum slope is emphasized throughout.Comment: 10 page

A clinical case of a combined method for correcting postkeratoplastic astigmatism of a high degree in a patient with cataract

Background. Performing penetrating keratoplasty in 100 % of cases leads to the occurrence of induced postkeratoplasty astigmatism, which can be more than 12,0 D. If cataracts occur in this category of patients, performing cataract phacoemulsification with implantation of a toric intraocular lens (tIOL) does not completely solve the problem. The use of the method of implantation of intrastromal corneal segments at stage I before cataract phacoemulsification makes it possible to reduce the degree of postkeratoplasty astigmatism and create optimal conditions for additional correction of residual postkeratoplasty astigmatism due to the implantation of tIOL during cataract phacoemulsification.The aim. To analyze the clinical and functional indicators of correction of regular high-grade postkeratoplasty astigmatism in a patient with cataracts using a combined method, including first implantation of intrastromal corneal segments and subsequent cataract phacoemulsification with implantation of toric intraocular lens using the example of a clinical case.Material and methods. A 55-year-old patient with cataracts, who had a history of  undergoing penetrating keratoplasty, contacted us. According to the keratotopogram data, a regular postkeratoplasty astigmatism of 18.68 D was diagnosed. The patient underwent a combined method. At stage I, intrastromal corneal segments were implanted into the corneal graft, then after 6 months stage II was performed – cataract phacoemulsification with implantation of tIOL.Results. Six months after intrastromal corneal segments implantation, the patient’s keratometric data stabilized, and corneal astigmatism decreased to 8.98 D. Then the patient underwent cataract phacoemulsification with tIOL implantation. After 1 month, the spherical component of refraction was 0.5 D, the cylindrical component of refraction was –0.5 D, visual acuity increased to 1.0.Conclusions. A combined method for correcting regular high-grade postkeratoplasty astigmatism in a patient with cataracts showed high refractive results, stability and safety in the long-term postoperative period

Comparative analysis of the correction of irregular postkeratoplastic astigmatism with scleral lenses and intrastromal ring implantation

Background. Many patients after penetrating keratoplasty (PK) experience induced postkeratoplastic astigmatism, which is often irregular and causes an increase in corneal aberrations that reduce visual acuity and quality. The aim of the study. To conduct a comparative analysis of the effect of rigid gas permeable scleral lenses and the MyoRing implantation method on clinical and functional parameters in patients with IPA. Material and methods. The clinical study included 60 patients (60 eyes). The age of patients with IPA was from 25 to 42 years. All patients underwent penetrating keratoplasty. All patients were divided into two groups depending on the method for irregular postkeratoplastic astigmatism correction. Group I included 30 patients (30 eyes) who were fitted with rigid gas permeable scleral lenses. Group II consisted of 30 patients (30 eyes) who underwent implantation of the MyoRing into a penetrating corneal graft. The observation period was 1 year. Results. After 12 months of observation, there was a greater increase in uncorrected visual acuity by an average of 3 lines, in corrected visual acuity – by 2 lines; a greater decrease in corneal aberrations in photo- (root mean square (RMS) of total aberrations (RMS total) by 0.30 ± 0.08 µm, RMS of higher order aberrations (RMS HOA) – by 1.01 ± 0.24 μm) and mesopic conditions (RMS total – by 0.33 ± 0.09 μm, RMS HOA – by 0.08 ± 0.03 μm) in patients wearing rigid gas permeable scleral lenses compared with patients after MyoRing implantation into a penetrating corneal graft. Conclusion. Patients of group  I, wearing rigid gas permeable scleral lenses, showed a greater improvement in visual acuity and a decrease in corneal aberrations in  photo- and mesopic conditions compared to the patients of group  II (after MyoRing implantation) at a follow-up period of 12 months

Quantum state preparation in circuit QED via Landau-Zener tunneling

We study a qubit undergoing Landau-Zener transitions enabled by the coupling to a circuit-QED mode. Summing an infinite-order perturbation series, we determine the exact nonadiabatic transition probability for the qubit, being independent of the frequency of the QED mode. Possible applications are single-photon generation and the controllable creation of qubit-oscillator entanglement.Comment: 7 pages, 3 figure