121055509
The quantum cosmology in the Brans-Dicke theory
In this paper, we try to establish the quantum cosmology based on the Brans-Dicke gravitational theory. The most remarkable property of it is that the scale factora(t) has a lower limit, where the cosmological wave function approaches zero.
43486042
Complex geometry, quantum tunneling, and time machines.
A space with a complex metric permitted by quantum cosmology is given; two regions, one containing no closed causal curve and one containing closed timelike curves, are separated by a complex region. Through quantum tunneling one can travel from one region to the other. The vacuum polarization stress-energy tensor converges everywhere so the space is stable. This challenges Hawking's chronology protection conjecture and highlights on building a time machine
120249108
Quantum-gravity interpretation of Brans-Cicke theory?the back-reaction of the vacuum matter field upon the Einstein space-time
A quantum gravity version is given to the Brans-Dicke theory. We find that the matter field quantum fluctuation induces the conformal quantum fluctuation of space-time, and that the latter backreacts to the classical space-time and transforms it from Einstein space-time into the Brans-Dicke one.
120532477
Thermodynamics of de Sitter universes
It is shown that the first law of thermodynamics can be applied to the de Sitter universe to relate its vacuum energy, pressure, entropy of horizon, chemical potential, etc., when the cosmological constant changes due to the fluctuation of the vacuum or other reasons. The second law should be reformulated in the form that the spontaneous decay of the vacuum never makes the entropy of the de Sitter universe decrease. The third law of thermodynamics, applying to the de Sitter universe, implies that the cosmological constant cannot reach zero by finite physical processes. The relation to the holographic principle is also briefly discussed.
120926032
Classical Instability of Anti-de Sitter Universe
This article discusses the gravitational stability of anti-de Sitter universe. It turns out that anti-de Sitter universe with closed timelike curves is unstable to gravitational perturbations.
121703876
Wormhole solution in Bergmann-Wagoner scalar-tensor gravitational theory
We give a Euclidean wormhole solution in the vacuum Bergmann-Wagoner scalar-tensor gravitational theory. We show that this wormhole, unlike others, has complex charge and is a baby universe (half a wormhole).
122741264
Quantum cosmology at finite temperature in superstring theory
We study cosmology induced by an ideal superstring gas at finite temperature. The thermal/quantum effects of the string gas generate a nontrivial effective potential at one-loop level. At certain points in the moduli space where generically massive states become massless, the effective potential develops local minima. The latter serve as moduli attractors, which induce time-dependent scalar masses decreasing in cosmological time. As a result, the coherent scalar oscillations dilute before nucleosynthesis, and the cosmological moduli problem is avoided. In particular, we study moduli stabilization in the cases of cosmology induced by i) a maximally supersymmetric heterotic string gas; ii) a gas of type II string compactified on Calabi-Yau three-folds. In case i), the local minima of the potential arise at enhanced gauge symmetry points, which can stabilize all moduli but the dilaton. In case ii), local minima of the effective potential are reached at the loci where 2-spheres or 3-spheres in the Calabi-Yau space shrink to zero size, giving rise to either conifold transitions or non Abelian gauge symmetries. Extra massless states are induced by D-brane wrapping the shrinking spheres, and the stabilized moduli are those controlling the volume of those spheres. In addition, in the two cases we also study respectively the type I dual theory which is maximally supersymmetric and the heterotic dual theory compactified on K3xT2. We show that dual moduli can be stabilized by novel non-perturbative effects implied by duality maps.
16860323
Rephasing Invariance and Hierarchy of the CKM Matrix
We identified a set of four rephasing invariant parameters of the CKM matrix. They are found to exhibit hierarchies in powers of λ 2 , from λ 2 to λ 8 . It is shown that, at the present level of accuracy, only the first three parameters are needed to fit all available data on flavor physics.
119388877
Energy absorption problem of a brane-world black hole
We have studied the wave dynamics and the energy absorption problem for the scalar field as well as the brane-localized gravitational field in the background of a brane-world black hole. Comparing our results with the four-dimensional Schwarzschild black hole, we have observed the signature of the extra dimension in the energy absorption spectrum.
119013315
PHENOMENOLOGY OF GOLDSTINO COUPLINGS
A general coupling of the Goldstino to the matter field and the weak gravitational field is constructed based on the standard and nonlinear Volkov–Akulov realization of SUSY. The resulting Lagrangian, which is invariant under SUSY transformations, can give rise to explicit interactions which couple the helicity ±1/2 states of the gravitino with the gravitational field as well as the matter field.
56166630
Centrality Dependence of Charged Particle Production at Large Transverse Momentum in Pb--Pb Collisions at $\sqrt{s_{\rm{NN}}} = 2.76$ TeV
The inclusive transverse momentum ($p_{\rm T}$) distributions of primary charged particles are measured in the pseudo-rapidity range $|\eta|<0.8$ as a function of event centrality in Pb--Pb collisions at $\sqrt{s_{\rm{NN}}}=2.76$ TeV with ALICE at the LHC. The data are presented in the $p_{\rm T}$ range $0.1530$ GeV/$c$. In peripheral collisions (70--80%), the suppression is weaker with $R_{\rm{AA}} \approx 0.7$ almost independently of $p_{\rm T}$. The measured nuclear modification factors are compared to other measurements and model calculations.