H-theorem in quantum physics

Remarkable progress of quantum information theory (QIT) allowed to formulate mathematical theorems for conditions that data-transmitting or data-processing occurs with a non-negative entropy gain. However, relation of these results formulated in terms of entropy gain in quantum channels to temporal evolution of real physical systems is not thoroughly understood. Here we build on the mathematical formalism provided by QIT to formulate the quantum H-theorem in terms of physical observables. We discuss the manifestation of the second law of thermodynamics in quantum physics and uncover special situations where the second law can be violated. We further demonstrate that the typical evolution of energy-isolated quantum systems occurs with non-diminishing entropy.Comment: 8 pages, 4 figure

Spatially inhomogeneous electron state deep in the extreme quantum limit of strontium titanate

When an electronic system is subjected to a sufficiently strong magnetic field that the cyclotron energy is much larger than the Fermi energy, the system enters the "extreme quantum limit" (EQL) and becomes susceptible to a number of instabilities. Bringing a three-dimensional electronic system deeply into the EQL can be difficult, however, since it requires a small Fermi energy, large magnetic field, and low disorder. Here we present an experimental study of the EQL in lightly-doped single crystals of strontium titanate, which remain good bulk conductors down to very low temperatures and high magnetic fields. Our experiments probe deeply into the regime where theory has long predicted electron-electron interactions to drive the system into a charge density wave or Wigner crystal state. A number of interesting features arise in the transport in this regime, including a striking re-entrant nonlinearity in the current-voltage characteristics and a saturation of the quantum-limiting field at low carrier density. We discuss these features in the context of possible correlated electron states, and present an alternative picture based on magnetic-field induced puddling of electrons.Comment: 8 pages, 5 figures, 7 pages of supplementary information; to appear in Nature Communication

Nova metoda rješavanja problema lomnog raspršenja Nd u konfiguracijskom prostoru

A new computational method for solving the configuration-space Faddeev equations for a three-nucleon system has been developed. This method is based on the spline-decomposition in the angular variable and on a generalization of the Numerov method for the hyperradius. The s-wave calculations of the inelasticity and phase-shift, as well as of the breakup amplitudes for nd and pd breakup scattering for lab energies 14.1 and 42.0 MeV have been performed using the Malfliet-Tjon MT I-III potential. In the case of nd breakup scattering, the results are in good agreement with those of the benchmark solution (J. L. Friar et al., Phys. Rev. C 42 (1990) 1838 and J. L. Friar et al., Phys. Rev. C 51 (1995) 2356). In the case of pd quartet breakup scattering, disagreement for the inelasticities reaches up to 6% when compared with the results of the Pisa group (A. Kievsky et al., Phys. Rev. C 64 (2001) 024002). The calculated pd amplitudes fulfill the optical theorem with a good precision.Razvili smo novu računalnu metodu za rješavanje Faddeevih jednadžbi u konfiguracijskom prostoru za sustav tri nukleona. Ona se zasniva na razvoju „spline“ po kutnoj varijabli i na poopćenoj Numerovoj metodi za hiperradijus. Računi neelastičnosti i faznih pomaka kao i amplituda loma za lomno raspršenje nd i pd na laboratorijskim energijama 14.1 i 42.0 MeV izvedeni su uz primjenu potencijala Malfliet -Tjon MT I-III. Za lomno raspršenje nd, ishodi računa su u dobrom skladu s ranijim rješenjima (J. L. Friar et al., Phys. Rev. C 42 (1990) 1838 i J. L. Friar et al., Phys. Rev. C 51 (1995) 2356). Za četvorno lomno raspršenje pd, razlike u neelastičnosti dosižu 6% u usporedbi s ishodima grupe u Pisi (A. Kievsky et al., Phys. Rev. C 64 (2001) 024002). Izračunate amplitude pd zadovoljavaju optički teorem s dobrom točnošću

Gell-Mann - Low Function in QED for the arbitrary coupling constant

The Gell-Mann -- Low function \beta(g) in QED (g is the fine structure constant) is reconstructed. At large g, it behaves as \beta_\infty g^\alpha with \alpha\approx 1, \beta_\infty\approx 1.Comment: 5 pages, PD

Spin Polarization Phenomena and Pseudospin Quantum Hall Ferromagnetism in the HgTe Quantum Well

The parallel field of a full spin polarization of the electron gas in a \Gamma8 conduction band of the HgTe quantum well was obtained from the magnetoresistance by three different ways in a zero and quasi-classical range of perpendicular field component Bper. In the quantum Hall range of Bper the spin polarization manifests in anticrossings of magnetic levels, which were found to strongly nonmonotonously depend on Bper.Comment: to be published in AIP Conf. Proc.: 15-th International Conference on Narrow Gap Systems (NGS-15