Black hole evolution in quantum-gravitational framework

We found black hole evolution on a quantum-gravitational scattering framework with an aim to tackle the black hole information paradox. With this setup, various pieces of the system information are explicit from the start and unitary evolution is manifest throughout. The scattering amplitudes factorize into the perturbative part and nonperturbative part. The nonperturbative part is dominated by an instanton-type contribution, i.e., a black hole analogue of the Coleman-De Luccia’s bounce solution, and we propose that the Hawking radiation be identified with the particles generated by the vacuum decay. Our results indicate that the black hole degrees of freedom are entangled not only with the Hawking modes but also with the pre-Hawking modes. The Wald’s entropy charge measures their entanglement. The full quantum-gravitational entropy is defined as the vev of the Wald entropy charge. With this definition a shifted Page-like curve is generically generated and its quantum extension is readily defined.

Two Sources of Paramagnetic Curie-Type Contribution to the Normal State Magnetic Susceptibility of HTSC YBa2Cu3O6+δ

The experimental evidence for the existence of chain paramagnetic Curie-type contribution to the temperature dependence of the normal (non-superconducting) state magnetic susceptibility χ (T) was obtained for pure high-Tc superconductors (HTSC) YBa2Cu3O6+δ series with different oxygen contents (0.6 < δ ≤ 1). It was shown that this contribution became clearly evident on curves χ (T) only at the temperature T < 150 K. It increases with the amount of oxygen vacancies increase in Cu1–O4 chains, and also depends on the way of the oxygen vacancies ordering.

INTERPLAY BETWEEN TRANSPORT, MAGNETIC-, AND STRUCTURAL PROPERTIES OF MN-PEROVSKITES WITH VARIOUS DOPING LEVEL

We performed a comparative study on the colossal negative magnetoresistivity and the Hall effect in thin films of the manganese perovskite La 1-x Ca x MnO 3 with x =0.3 and x =0.67. The underdoped sample ( x =0.3) undergoes a phase transition from a paramagnetic semiconductor to a ferromagnetic quasimetal at the Curie temperature T C =280 K , while the overdoped compound ( x =0.67) stays a paramagnetic semiconductor at all temperatures. Both materials show colossal negative magneto-resistivity, albeit on considerably different temperature- and field scales, depending on the magnetic interactions between neighbouring Mn ions. According to the Hall data, the charge carriers in the underdoped material are hole-type, partially compensated by an electron-type contribution. The overdoped system shows electronic carriers with a thermally activated concentration. The ordinary Hall effect is in both compounds superimposed by an anomalous Hall contribution with a sign opposite to the intrinsic charge-carrier type.