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In this paper, we systematically study the work statistics for quantum phase transition. For a quantum system approached by an anisotropic conformal field theory near the critical point, the driving protocols is divided into three different regimes for different quench rates, which reflects the competition between the frozen time and the quench time scale. In each regime, we find universal scaling behaviors in work statistics (after renormalization). It is shown that the critical exponents are determined by the space-time dimension $d$, the dynamical critical exponent $z$, the correlation-length exponent $\nu$, and the power-law protocols. These universal scalings in nonequilibrium process may be found in quantum phase transition by measuring the Loschmidt echo or the Ramsey interferometry.

For Hawking radiation, treated as a tunneling process, the no-hair theorem of black hole together with the law of energy conservation is utilized to postulate that the tunneling rate only depends on the external qualities (e.g., the mass for the Schwarzschild black hole) and the energy of the radiated particle. This postulate is justified by the WKB approximation for calculating the tunneling probability. Based on this postulate, a general formula for the tunneling probability is derived without referring to the concrete form of black hole metric. This formula implies an intrinsic correlation between the successive processes of the black hole radiation of two or more particles. It also suggests a kind of entropy conservation and thus resolves the puzzle of black hole information loss in some sense., Comment: 4pages,1 figure

We study how to recover the unitarity of Lee model with the help of bi-orthogonal basis approach, when the physical coupling constant in renormalization exceeds its critical value, so that the Lee's Hamiltonian is non-Hermitian with respect to the conventional inner product. In a very natural fashion, our systematic approach based on bi-orthogonal basis leads to an elegant definition of inner product with a non-trivial metric, which can overcome all the previous problems in Lee model, such as non-Hermiticity of the Hamiltonian, the negative norm, the negative probability and the non-unitarity of the scattering matrix., Comment: 9 pages, 5 figures

We make a novel observation about the decoherence phenomenon of the fermion in the Witten's supersymmetric (SUSY) quantum mechanical model. It is shown that, when the bosonic partner in the SUNY model is unobservable in a certain energy scale, the quantum coherence meant by the superposition of fermion states can not be preserved for a long time due to the quantum decoherence induced by the overlooked boson. This refers to a supercharge superselection rule similar to the charge superselection. We numerically calculate the decoherence factor characterizing the extent of decoherence . The obtained result shows the periodic decoherence with finite quantum jump. Some analytic results under the harmonic approximation for the superpotential can be obtained to confirm the numerical calculations., Comment: 14 pages, 3 figures

By using a two-mode description, we show that there exist the multistability, phase transition and associated critical fluctuations in the macroscopic tunneling process between the halves of a double-well trap containing a Bose-Einstein condenstate. The phase transition that two of the triple stable states and a unstable state merge into one stable state or a reverse process takes place whenever the ratio of the mean field energy per particle to the tunneling energy goes across a critical value of order one. The critical fluctuation phenomenon corresponds to squeezed states for the phase difference between the two wells accompanying with large fluctuations of atom numbers., Comment: 4 page, with 1 Figure,Revtex

By using a two-mode description, we show that there exist the multistability, phase transition and associated critical fluctuations in the macroscopic tunneling process between the halves of a double-well trap containing a Bose-Einstein condenstate. The phase transition that two of the triple stable states and a unstable state merge into one stable state or a reverse process takes place whenever the ratio of the mean field energy per particle to the tunneling energy goes across a critical value of order one. The critical fluctuation phenomenon corresponds to squeezed states for the phase difference between the two wells accompanying with large fluctuations of atom numbers., Comment: 4 page, with 1 Figure,Revtex

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, Latex

In the view of the quantum dynamic theory of measurement developed from the Hepp-Colemen (HC) model (K. Hepp, Hev.Phys.Acta, {\bf 45}, 237 (1972)), the quantum decoherence in neutrino flavor oscillation caused by an environment surrounding neutrinos is generally considered in this paper. The Ellis, Hagelin, Nanopoulos and Srednicki (EHNS) mechanism for solving the solar neutrino problem can be comprehended in a framework of the ordinary quantum mechanics. In the weak- coupling limit, a microscopic model is proposed to describe the transition of two neutrino system from a pure state to a mixed state. It gives the modified formula of survival probability of neutrino oscillation with two additional time-dependent parameters. For specified environments, this result shows that the oscillating phenomena of neutrino still exist even without a mass difference in free neutrino., Comment: Revtex 4 pages, address: Institute of Theoretical Physics, Academia Sinica, Beijing, China; www: http://www.itp.ac.cn/~suncp

In the view of the quantum dynamic theory of measurement developed from the Hepp-Colemen (HC) model (K. Hepp, Hev.Phys.Acta, {\bf 45}, 237 (1972)), the quantum decoherence in neutrino flavor oscillation caused by an environment surrounding neutrinos is generally considered in this paper. The Ellis, Hagelin, Nanopoulos and Srednicki (EHNS) mechanism for solving the solar neutrino problem can be comprehended in a framework of the ordinary quantum mechanics. In the weak- coupling limit, a microscopic model is proposed to describe the transition of two neutrino system from a pure state to a mixed state. It gives the modified formula of survival probability of neutrino oscillation with two additional time-dependent parameters. For specified environments, this result shows that the oscillating phenomena of neutrino still exist even without a mass difference in free neutrino., Comment: Revtex 4 pages, address: Institute of Theoretical Physics, Academia Sinica, Beijing, China; www: http://www.itp.ac.cn/~suncp