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Yu. E. Kuzovlev

Publications and source records attributed to Yu. E. Kuzovlev.

33 records · Page 2Linked to original sources
arXiv2011

Electron random walk in ideal phonon gas. Spectra of density matrix evolution and electron mobility 1/f noise

The previously derived exact evolution equations for density matrix of electron (quantum particle) in phonon field (boson thermostat) are qualitatively analysed. Their statistical interpretation is explained in detail, and their main symmetry and spectral properties are expounded. In application to the electron's random walk, it is shown that these properties certaimly forbid conventionally assumed Gaussian long-range asymptotic of the walk statistics. Instead, the exact equations imply super-linear dependence of fourth-order cumulant of total electron's path on observation time, which signifies existence of 1/f-type low-frequency fluctuations in electro's diffusivity and mobility. Physical meaning of this result is discussed, along with general origin of 1/f-noise in classical and quantum Hamiltonian many-particle systems.

cond-mat.stat-mech↗
arXiv2011

Some comments to the quantum fluctuation theorems

It is demonstrated that today's quantum fluctuation theorems are component part of old quantum fluctuation-dissipation relations [Sov.Phys.-JETP 45, 125 (1977)], and typical misunderstandings in this area are pointed out.

cond-mat.stat-mech↗
arXiv2011

Electron random walk in ideal phonon gas. Exact dressed electron density matrix evolution equations

An original approach is suggested to analysis of full quantum Liouville equation for single electron (quantum particle) interacting with ideal phonon gas (harmonic boson thermostat). It is shown that under the thermodynamic limit this equation can be exactly reduced to a system of evolution equations connecting density matrix of the electron and its simplest irreducible correlations with amplitudes of one, two, three and more phonon modes. Possible application of these new equations to explanation of the electron mobility 1/f-type fluctuations in semiconductors and other media is discussed. The special case of electron in static disorder is also considered.

cond-mat.stat-mech↗
arXiv2011

Once again on molecular Brownian motion and related fundamental 1/f noise: a logical analysis of exact equations

The paper contains a simple semi-quantitative analysis of a structure of solution to the exact Bogolyubov functional equation for a particle interacting with ideal gas and driven by an external force, in comparison with solutions to model kinetic equations for the same system. It is shown that the exact equation inevitably predicts existence of significant 1/f-type fluctuations in mobility of the particle, and this result directly extends to particles in arbitrary fluid.

cond-mat.stat-mech↗
arXiv2010

On statistics and 1/f noise of molecular random walk in low-density gas

The random walk of test particle in low-density gas is considered basing on approximate coarsened version of the collisional representation of the BBGKY equations. The coarsening presumes that momentum relaxation rates of the test particle and gas atoms are equal but allows to analyze the case when their masses are different. It is shown that both the spectrum exponent and probability distribution of 1/f-type diffusivity fluctuations of the test particle essentially depend on ratio of the masses, and corresponding distribution of its path is found.

cond-mat.stat-mech↗
arXiv2009

A lemma about molecular chaos

Solutions to the BBGKY hierarchy of equations for molecular Brownian particle in ideal gas are considered, and exact relations are derived between probability distribution of path of the particle, its derivatives in respect to gas density and irreducible many-particle correlations of gas atoms with the path. It is shown that all the correlations always give equally important contributions to evolution of the path distribution, and therefore the exact statistical mechanics theory does not reduce to classical kinetics even in the low-density limit.

math-ph↗
arXiv2008

Thermodynamic restrictions on statistics of molecular random walks

It is shown that time reversibility of Hamiltonian microscopic dynamics and Gibbs canonical statistical ensemble of initial conditions for it together produce an exact virial expansion for probability distribution of path of molecular Brownian particle in a fluid. This expansion leads to inequality connecting logarithmic derivative of the distribution with respect to fluid density and characteristic volume occupied by pair statistical correlation between the path and fluid molecules. Due to the inequality, finiteness of this volume means that asymptotic of the distribution is essentially non-Gaussian. For principal case when fluid is dilute gas it is demonstrated that the pair correlation volume is actually finite and bounded above. Therefore even under the Boltzmann-Grad limit the path distribution possess power-law long tails (cut off at distances of ballistic flight).

cond-mat.stat-mech↗
arXiv2006

Designing Langevin microdynamics in macrocosm

Previously developed ``stochastic representation of deterministic interactions`` enables exact treatment of an open system without leaving its native phase space (Hilbert space) due to peculiar stochastic extension of the Liouville (von Neumann) equation for its statistical operator. Can one reformulate the theory in terms of stochastic ``Langevin equations'' for its variables? Here it is shown that in case of classical Hamiltonian underlying dynamics the answer is principally positive, and general explicit method of constructing such equations is described.

cond-mat.stat-mech↗
arXiv2003

Stochastic representation of quantum interactions and two-lewel systems

Stochastic representation for interaction of quantum systems is formulated which allows to replace some of them by equivalent but purely commutative random sources. The formalism is applied to two-level systems interacting with Gaussian thermal bath. Strong-coupling non-Marcovian effects and besides long-living fluctuations in common susceptibility of two systems subjected to the same bath are considered.

cond-mat.stat-mech↗
arXiv2000

Quantum discreteness and fundamental 1/f noise in tunnel junctions, nano-composites and other many-electron systems

It is shown, with citing tunnel junction as an example, that mutual interplay of electron quantum transfers in a conducting system can be the fast mechanism for generation fundamental low-frequency flicker conductance fluctuations (1/f noise) without composing Lorentzians. This effect is lost in a theory which neglects the actual discreteness of electron energy levels. The analytical estimates of fluctuations of tunnel conductance are obtained, and the strong 1/f-noise sensibility to the discreteness as observed in nano-composites is explained both qualitatively and quantitatively.

cond-mat.stat-mech↗
arXiv2000

Fast fluctuating fields as the source of low-frequency conductance fluctuations in many-electron systems and failure of quantum kinetics

It is shown that in many-electron systems quantum transfer amplitudes and thus transfer probabilities may be strongly influenced by fast fluctuating fields, in particular, caused by simultaneous electron transfers. Corresponding mutual interplay of many electron jumps, arising at the fundamental level of quantum phases, results in long-correlated (1/f type) conductance fluctuations. However, thats could not be theoretically catched if neglect the real discreteness of quantum energy spectra and use the continuous spectrum approximation when building kinetic theory. Basing on first principles, the estimates of low-frequency fluctuations of tunneling conductance are presented.

cond-mat.stat-mech↗
arXiv1999

Penetration and transformations of vortices in bulk current-carrying superconductors

The equations of viscous evolution of 3D arbitrarily shaped vortices in an isotropic type II superconductor and necessary boundary conditions are formulated in the frame of London approximation. The theory is applied to analyse characteristic scenaria of vortex penetration into current-carrying thick plate or bulk samples with another geometry. It is shown that regarding of the surface transport current value a vortex penetrates either as "flexible stick" or as "elastic thread". The latter regime is accompanied by giant stretching of the vortex core along the current-induced surface magnetic field. This geometrical transformation leads to decrease of viscous friction and large increase of the vortex drift velocity as compared with the stick-like regime. As a result, the vortex first winds round the sample cross-section and forms a ring-like curve, and only later begins to move deep into the sample interior. The analytical estimates of the vortex shape and stretching and its velocity are obtained.

cond-mat.supr-con↗