Biomedical subjects

Dmitry L Dorofeev

Publications and source records attributed to Dmitry L Dorofeev.

5 recordsLinked to original sources

PubMed2006

Fluctuations and transients in quantum-resonant evolution.

The quantum-resonant evolution of the mean kinetic energy (MKE) of the kicked particle is studied in detail on different time scales for general periodic kicking potentials. It is shown that the asymptotic time behavior of a wave-packet MKE is typically a linear growth with bounded fluctuations having a simple number-theoretical origin. For a large class of wave packets, the MKE is shown to be exactly the superposition of its asymptotic behavior and transient logarithmic corrections. Both fluctuations and transients can be significant for not too large times but they may vanish identically under some conditions. In the case of incoherent mixtures of plane waves, it is shown that the MKE never exhibits asymptotic fluctuations but transients usually occur.

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PubMed2006

General quantum resonances of the kicked particle.

The quantum resonances (QRs) of the kicked particle are studied in a most general framework by also considering arbitrary periodic kicking potentials. It is shown that QR can arise, in general, for any rational value of the Bloch quasimomentum. This is illustrated in the case of the main QRs for arbitrary potentials. In this case, which is shown to be precisely described by the linear kicked rotor, exact formulas are derived for the diffusion coefficients determining the asymptotic evolution of the average kinetic energy of either an incoherent mixture of plane waves or a general wave packet. The momentum probability distribution is exactly calculated and studied for a two-harmonic potential. It clearly exhibits additional resonant values of the quasimomentum and it is robust under small deviations from QR.

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PubMed2005

General approach to the quantum kicked particle in a magnetic field: quantum-antiresonance transition.

The quantum kicked particle in a magnetic field is studied in a weak-chaos regime under realistic conditions, i.e., for general values of the conserved coordinate x(c) of the cyclotron orbit center. The system exhibits spectral structures ["Hofstadter butterflies" (HBs)] and quantum diffusion depending sensitively on x(c). Most significant changes take place when x(c) approaches the value at which quantum antiresonance (exactly periodic recurrences) can occur: the HB essentially "doubles" and the quantum-diffusion coefficient D(x(c)) is strongly reduced. An explanation of these phenomena, including an approximate formula for D(x(c)) in a class of wave packets, is given on the basis of an effective Hamiltonian which is derived as a power expansion in a small parameter. The global quantum diffusion of a two-dimensional wave packet for all x(c) is briefly considered.

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PubMed2005

Nonlinear magnetoacoustic waves in rare-earth orthoferrites.

The dynamics of magnetoacoustic waves in a rare-earth orthoferrite YFeO3 crystal is experimentally investigated. The waves are excited by a high-power laser pulse. The analysis of results is carried out taking into account the nonlinear interaction of oscillation modes. It allows us to interpret the results as energy exchange between modes in the time scale, a phenomenon known in nonlinear optics. Based on the proposed model an estimation is obtained for effective nonlinear magnetoacoustic modules of fourth order for yttrium orthoferrite approximately 2.5x 10(17) -2.5x 10(19) J/ m(3) .

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PubMed2003

Tolman's nonlinearity of capillary waves.

A nonlinear theory of nanometer capillary waves is developed that takes curvature dependence of the surface tension coefficient (Tolman's nonlinearity) into account. Estimations are given that indicate the importance of Tolman's nonlinearity for thermocapillary waves.

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