The arrow of time: from universe time-asymmetry to local irreversible processes

In several previous papers we have argued for a global and non-entropic approach to the problem of the arrow of time, according to which the ''arrow'' is only a metaphorical way of expressing the geometrical time-asymmetry of the universe. We have also shown that, under definite conditions, this global time-asymmetry can be transferred to local contexts as an energy flow that points to the same temporal direction all over the spacetime. The aim of this paper is to complete the global and non-entropic program by showing that our approach is able to account for irreversible local phenomena, which have been traditionally considered as the physical origin of the arrow of time.Comment: 48 pages, 8 figures, revtex4. Accepted for publication in Foundations of Physic

Functional Approach to Quantum Decoherence and the Classical Final Limit

For a wide set of quantum systems it is demonstrated that the quantum regime can be considered as the transient phase while the final classical statistical regime is a permanent state. A basis where exact matrix decoherence appears for these final states is found. The relation with the decoherence of histories formalism is studied. A set of final intrinsically consistent histories is found.Comment: 20 pages. Phys. Rev A in press 200

Thermal Conditions for Scalar Bosons in a Curved Space Time

The conditions that allow us to consider the vacuum expectation value of the energy-momentum tensor as a statistical average, at some particular temperature, are given. When the mean value of created particles is stationary, a planckian distribution for the field modes is obtained. In the massless approximation, the temperature dependence is as that corresponding to a radiation dominated Friedmann-like model.Comment: 14 pages (TeX manuscript

Decoherence time in self-induced decoherence

A general method for obtaining the decoherence time in self-induced decoherence is presented. In particular, it is shown that such a time can be computed from the poles of the resolvent or of the initial conditions in the complex extension of the Hamiltonian's spectrum. Several decoherence times are estimated: $10^{-13}-$ $10^{-15}s$ for microscopic systems, and $10^{-37}-10^{-39}s$ for macroscopic bodies. For the particular case of a thermal bath, our results agree with those obtained by the einselection (environment-induced decoherence) approach.Comment: 11 page

A Unified Conformal Model for Fundamental Interactions without Dynamical Higgs Field

A Higgsless model for strong, electro-weak and gravitational interactions is proposed. This model is based on the local symmetry group SU(3)xSU(2)xU(1)xC where C is the local conformal symmetry group. The natural minimal conformally invariant form of total lagrangian is postulated. It contains all Standard Model fields and gravitational interaction. Using the unitary gauge and the conformal scale fixing conditions we can eliminate all four real components of the Higgs doublet in this model. However the masses of vector mesons, leptons and quarks are automatically generated and are given by the same formulas as in the conventional Standard Model. The gravitational sector is analyzed and it is shown that the model admits in the classical limit the Einsteinian form of gravitational interactions. No figures.Comment: 25 pages, preprin

A time-dependent perturbative analysis for a quantum particle in a cloud chamber

We consider a simple model of a cloud chamber consisting of a test particle (the alpha-particle) interacting with two other particles (the atoms of the vapour) subject to attractive potentials centered in $a_1, a_2 \in \mathbb{R}^3$. At time zero the alpha-particle is described by an outgoing spherical wave centered in the origin and the atoms are in their ground state. We show that, under suitable assumptions on the physical parameters of the system and up to second order in perturbation theory, the probability that both atoms are ionized is negligible unless $a_2$ lies on the line joining the origin with $a_1$. The work is a fully time-dependent version of the original analysis proposed by Mott in 1929.Comment: 23 page

Statistical Mechanics for Unstable States in Gel'fand Triplets and Investigations of Parabolic Potential Barriers

Free energies and other thermodynamical quantities are investigated in canonical and grand canonical ensembles of statistical mechanics involving unstable states which are described by the generalized eigenstates with complex energy eigenvalues in the conjugate space of Gel'fand triplet. The theory is applied to the systems containing parabolic potential barriers (PPB's). The entropy and energy productions from PPB systems are studied. An equilibrium for a chemical process described by reactions $A+CB\rightleftarrows AC+B$ is also discussed.Comment: 14 pages, AmS-LaTeX, no figur

Predição do consumo de matéria seca de cabras leiteiras durante a gestação.

Resumo: O período da gestação é caracterizado por importantes mudanças fisiológicas no corpo materno tais como a diminuição da ingestão de alimento no último terço de gestação em fêmeas com gestação de múltiplos fetos. O objetivo desse estudo foi desenvolver modelos para predizer a ingestão de matéria seca (IMS) em cabras durante gestação simples e gemelar. Parar este estudo, foram usadas 1820 observações de IMS, obtidos diariamente a partir de sete cabras com gestação gemelar e seis cabras com gestação simples a partir do primeiro dia até os 140 dias de gestação. A IMS diária foi ajustada em três modelos não lineares, os quais foram avaliados através do critério de informação Bayesiana (BIC) como um indicador de melhor ajuste do modelo aos dados. O modelo que melhor se ajustou aos dados foi o modelo quadrático, com valor de BIC de 11549. Os interceptos e coeficientes de regressões do modelo quadrático utilizado para predição do IMS diário foram diferentes entre gestação simples e gemelar (P< 0.01). Comparado as cabras com gestação simples, as cabras com gestação gemelar tiveram maior decréscimo na IMS durante a gestação. Esse decréscimo na IMS em fêmeas com gestação gemelar se deve principalmente a mudanças hormonais e a maior compressão ruminal causada pelo maior tamanho de seus úteros grávidos. Os modelos desenvolvidos nesse estudo devem de ser considerados no manejo nutricional de cabras leiteiras durante a gestação. [Prediction of dry matter intake of dairy goats during pregnancy]. Abstract: The pregnancy is characterized by important physiological changes in maternal body such as a decrease on feed intake in the last third of pregnancy mainly in pregnancy of multiples fetuses. The objective of this study was to develop a model to predict the dry matter intake (DMI) of dairy goats carrying single and twin fetuses throughout pregnancy. For this study it was used a total of 1820 individual records of DMI from seven goats carrying twins and six goats carrying single fetuses. The DMI was daily recorded from the first up to 140 days of pregnancy. The daily DMI as a proportion of the average BW was fitted to tree non-linear models which were evaluated considering the Bayesian information criterion (BIC) value as an indicator how well the model fit the data. The best model fitting the data was the quadratic model with had BIC value of 11549. The intercepts and the slopes of the quadratic models used to predict the daily DMI were different between litter sizes (P < 0.01). Goats carrying twin fetuses showed a greater decrease in the DMI during pregnancy compared to goats carrying single fetus. The decrease of feed intake in females carrying twins may be mainly related to hormonal changes and a greatest rumen compression due to the biggest size of the gravid uterus. The models developed in this study may be relevant in the adoption of nutritional management of dairy goats during the pregnancy

Third quantization of f(R)f(R)-type gravity

We examine the third quantization of $f(R)$-type gravity, based on its effective Lagrangian in the case of a flat Friedmann-Lemaitre-Robertson-Walker metric. Starting from the effective Lagrangian, we execute a suitable change of variable and the second quantization, and we obtain the Wheeler-DeWitt equation. The third quantization of this theory is considered. And the uncertainty relation of the universe is investigated in the example of $f(R)$-type gravity, where $f(R)=R^2$. It is shown, when the time is late namely the scale factor of the universe is large, the spacetime does not contradict to become classical, and, when the time is early namely the scale factor of the universe is small, the quantum effects are dominating.Comment: 9 pages, Arbitrary constants in (4.19) are changed to arbitrary functions of $\varphi$. Conclusions are not changed. References are added. Typos are correcte

The Isaacson expansion in quantum cosmology

This paper is an application of the ideas of the Born-Oppenheimer (or slow/fast) approximation in molecular physics and of the Isaacson (or short-wave) approximation in classical gravity to the canonical quantization of a perturbed minisuperspace model of the kind examined by Halliwell and Hawking. Its aim is the clarification of the role of the semiclassical approximation and the backreaction in such a model. Approximate solutions of the quantum model are constructed which are not semiclassical, and semiclassical solutions in which the quantum perturbations are highly excited.Comment: Revtex, 11 journal or 24 preprint pages. REPLACEMENT: A comment on previous work by Dowker and Laflamme is corrected. Utah preprint UU-REL-93/3/1