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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
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
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