Consequences of 't Hooft's Equivalence Class Theory and Symmetry by Large Coarse Graining

According to 't Hooft (Class.Quantum.Grav. 16 (1999), 3263), quantum gravity can be postulated as a dissipative deterministic system, where quantum states at the ``atomic scale''can be understood as equivalence classes of primordial states governed by a dissipative deterministic dynamics law at the ``Planck scale''. In this paper, it is shown that for a quantum system to have an underlying deterministic dissipative dynamics, the time variable should be discrete if the continuity of its temporal evolution is required. Besides, the underlying deterministic theory also imposes restrictions on the energy spectrum of the quantum system. It is also found that quantum symmetry at the ``atomic scale'' can be induced from 't Hooft's Coarse Graining classification of primordial states at the "Planck scale".Comment: 12 papge, Late

Heat transport of La2−y_{2-y}Euy_yCuO4_4 and La1.88−y_{1.88-y}Euy_ySr0.12_{0.12}CuO4_4 single crystals

To study the rare-earth doping effect on the phonon heat transport of La-based cuprates and shed light on the mechanism of phonon scattering, both $ab$-plane and c-axis thermal conductivities ($\kappa_{ab}$ and $\kappa_c$) are measured for La$_{2-y}$Eu$_y$CuO$_4$ ($y$ = 0, 0.02 and 0.2) and La$_{1.88-y}$Eu$_y$Sr$_{0.12}$CuO$_4$ ($y$ = 0 and 0.2) single crystals. It is found that the phonon peak (at 20 -- 25 K) in $\kappa_{ab}(T)$ of La$_{2-y}$Eu$_y$CuO$_4$ shows an anomalous Eu-doping dependence: it completely disappears for $y$ = 0.02, which is discussed to be due to the local lattice distortions around Eu dopants, and reappears for $y$ = 0.2 with much smaller peak magnitude compared to $y$ = 0 sample. In contrast to the strong suppression of the phonon peak in Eu-doped La$_2$CuO$_4$, Eu-doping to La$_{1.88}$Sr$_{0.12}$CuO$_4$ enhances the low-$T$ phonon heat transport that results in the reappearance of the phonon peak in this charge-carrier-doped system. The data clearly show that the establishment of static stripe phase rather than the structural change is responsible for the reappearance of phonon peak.Comment: 7 pages, 5 figures, final version published in Phys. Rev.

Metal-to-Insulator Crossover in YBa_{2}Cu_{3}O_{y} Probed by Low-Temperature Quasiparticle Heat Transport

It was recently demonstrated that in La_{2-x}Sr_{x}CuO_{4} the magnetic-field (H) dependence of the low-temperature thermal conductivity \kappa up to 16 T reflects whether the normal state is a metal or an insulator. We measure the H dependence of \kappa in YBa_{2}Cu_{3}O_{y} (YBCO) at subkelvin temperatures for a wide doping range, and find that at low doping the \kappa(H) behavior signifies the change in the ground state in this system as well. Surprisingly, the critical doping is found to be located deeply inside the underdoped region, about the hole doping of 0.07 hole/Cu; this critical doping is apparently related to the stripe correlations as revealed by the in-plane resistivity anisotropy.Comment: 4 pages, 3 figures; minor revision, accepted for publication in Phys. Rev. Let

Localization of Macroscopic Object Induced by the Factorization of Internal Adiabatic Motion

To account for the phenomenon of quantum decoherence of a macroscopic object, such as the localization and disappearance of interference, we invoke the adiabatic quantum entanglement between its collective states(such as that of the center-of-mass (C.M)) and its inner states based on our recent investigation. Under the adiabatic limit that motion of C.M dose not excite the transition of inner states, it is shown that the wave function of the macroscopic object can be written as an entangled state with correlation between adiabatic inner states and quasi-classical motion configurations of the C.M. Since the adiabatic inner states are factorized with respect to each parts composing the macroscopic object, this adiabatic separation can induce the quantum decoherence. This observation thus provides us with a possible solution to the Schroedinger cat paradoxComment: Revtex4,23 pages,1figur