Thermodynamics of the Bulk Viscous Cosmological Fluid in Presence of the Particle Creation Pressure

In the present work, we consider FRW metric and investigate some cosmological quantities in presence of bulk viscosity and particle creation pressure. The obtained results for a viscous cosmological fluid with particle creation show that the Hubble expansion parameter, energy density, bulk viscosity pressure, creation pressure and temperature depend on the particle creation rate and increase with increasing particle creation coefficient. It is found that the bulk viscosity and particle creation pressure seem to play important roles in the evolution of the early Universe.     

Creation of vector bosons by an electric field in curved spacetime

We investigate the creation rate of massive spin-1 bosons in the de Sitter universe by a time-dependent electric field via the Duffin–Kemmer–Petiau (DKP) equation. Complete solutions are given by the Whittaker functions and particle creation rate is computed by using the Bogoliubov transformation technique. We analyze the influence of the electric field on the particle creation rate for the strong and vanishing electric fields. We show that the electric field amplifies the creation rate of charged, massive spin-1 particles. This effect is analyzed by considering similar calculations performed for scalar and spin-1/2$1/2$ particles.     

The inhomogeneous quantum invariance group of commuting fermions

We consider a model of d fermions where creation and annihilation operators of different fermions commute. We show that this particle algebra is invariant under an inhomogeneous quantum group.      

Determination of the top quark mass through the measurement of the\frac{{\Gamma ({\rm Z} \to b\bar b)}}{{\Gamma _{hadr} - \Gamma (Z \to b\bar b)}} ratio at high luminosity LEP

We investigate a possible role of invariant (the integral of motion) in nonstationary field theory by employing an explicit example of a scalar field interacting with a time-dependent external electromagnetic field. We show how in a unique manner the invariant operator leads to the particle concept in the Schrödinger picture. This approach gives an intermediate connection between the operator and functional-Schrödinger-equation formalisms. An application to the problem of particle creation is also discussed briefly.     

Letter: Adiabatic Decaying Vacuum Model for the Universe

We study a model that the entropy per particle in the universe is constant. The sources for the entropy are the particle creation and a decaying term. We find exact solutions for the Einstein field equations and show the compatibility of the model with respect to the age and the acceleration of the universe.     

Particle creation if a cosmic string snaps

We calculate the Bogolubov coefficients for aC ⁽⁰⁾ metric which describes the snapping of a cosmic string. In this background, we show that there are noregular solutions with particle interpretation, but we find ageneralized solution with integrable discontinuity, which exhibits particle creation. We also find a regular solution if we allow wave packets.     

Cosmological Models with Bulk Viscosity in the Presence of Particle Creation

The effect of bulk viscosity, with a time varying bulk viscous coefficient, on the evolution of frw models is investigated in the context of open thermodynamic systems, which allows for particle creation. It is seen that, by choosing an appropriate function for particle creation, the models presented exhibit non-singular beginnings.     

Bemerkungen zur Teilchenerzeugung im expandierenden Universum

Remarks to the Creation of Particles in an Expanding Universe It is shown that one can get spontaneous particle creation in an empty Minkowskispace, if one defines particle-number operator and Hilbert space in a similar way as in publications about particle creation in an expanding universe [1–3]. Accordingly spontaneous particle creation does not originate in the gravitational field, but is connected with the non-uniqueness of the notion “particle” and the chosen timedependent particle-number operator. Es ist in den letzten Jahren von mehreren Autoren [1, 2, 3] die Möglichkeit der spontanen Erzeugung von Teilchen aus dem Vakuum in einem expandierenden Universum in Betracht gezogen worden. Von HAWKING [4] und TREDER [5, 6] wurde näher untersucht, inwieweit sich eine solche Teilchenerzeugung mit rein klassischen Argumenten ad absurdum führen läßt. So folgt allein aus der Bedingung der Energie-dominanz [4]     

Theoretical study of the trapping efficiency of an optical tweezers array system

Optical tweezers have been a valuable research tool since their invention in the 1980s. One of the most important developments in optical tweezers in recent years is the creation of two-dimensional arrays of optical traps. In this paper, a method based on interference is discussed to form gradient laser fields, which may cause the spatial modulation of particle concentration. The parameters related to the optical tweezers array are discussed in detail and simulated by the Matlab software to show the influence of important parameters on the distribution of particle concentration. The spatial redistribution of particles in a laser interference field can also be predicted according to the theoretical analysis.     

Creation of particles by time-dependent gravitational fields

A method based on the formulation of a quantum equivalence principle is introduced in order to define particle annihilation and creation operators during the expansion of the universe. Our theory predicts the creation of a finite number of particles.     

Gravitationally induced particle creation in aq-scalar field

Tom and Goodison [5] have shown that for generic values ofq, gravitationally induced particle creation is impossible in the ordinary vacuum state. Here we consider the evolution of aq-deformed scalar field in a curved spacetime and observe that if the field is either represented by a coherent state or a squeezed state, there is a change in the energy density of the field indicating the possibility of particle creation.     

On tunneling through the black hole horizon

It is shown here that there is no way for particle creation to occur by quantum tunneling through an infinitesimal neighborhood of the black hole horizon. This result is a trivial consequence of the regularity of the horizon, the equivalence principle and the general covariance of the relativistic theory of gravity. Moreover, we also confirm the less trivial statement that no particle creation by quantum tunneling through the black hole horizon is possible independent of the size of the presupposed tunneling domain.     

On particle creation by black holes

Hawking's analysis of particle creation by black holes is extended by explicitly obtaining the expression for the quantum mechanical state vector ψ which results from particle creation starting from the vacuum during gravitational collapse. (Hawking calculated only the expected number of particles in each mode for this state.) We first discuss the quantum field theory of a Hermitian scalar field in an external potential or in a curved but asymptotically flat spacetime with no horizon present. In agreement with previously known results, we find that we are led to a unique quantum scattering theory which is completely well behaved mathematically provided a certain condition is satisfied by the operators which describe the scattering of classical positive frequency solutions. In terms of these operators we derive the expression for the state vector describing particle creation from the vacuum, and we prove that S-matrix is unitary. Making the necessary modification for the case when a horizon is present, we apply this theory for a massless Hermitian scalar field to get the state vector describing the steady state emission at late times for particle creation during gravitational collapse to a Schwarzschild black hole. There is some ambiguity in the theory in this case arising from freedom involved in defining what one means by “positive frequency” at the future event horizon. However, it is proven that the expression for the density matrix formed from ψ describing the emission of particles to infinity is independent of this choice, and thus unambiguous predictions for the results of all possible measurements at infinity are obtained. We find that the state vector describing particle creation from the vacuum decomposes into a simple product of state vectors for each individual mode. The density matrix describing emission of particles to infinity by this particle creation process is found to be identical to that of black body emission. Thus, black hole emission agrees in complete detail (i.e., not only in expected number of particles) with black body emission.     

Cosmological models with particle creation and bulk viscosity

The effect of bulk viscosity on the evolution of the Friedmann models is investigated in the context of open thermodynamic systems, which allows for particle creation. It is seen that, by choosing an appropriate function,(t), for the particle creation, all the models presented exhibit inflationary expansion and a non-singular beginning.     

Tricriticality in generalized Schloegl models for autocatalysis: Lattice-gas realization with particle diffusion

We analyze lattice-gas reaction-diffusion models which include spontaneous annihilation, autocatalytic creation, and diffusion of particles, and which incorporate the particle creation mechanisms of both Schloegl’s first and second models. For fixed particle diffusion or hop rate, adjusting the relative strength of these creation mechanisms induces a crossover between continuous and discontinuous transitions to a “poisoned” vacuum state. Kinetic Monte Carlo simulations are performed to map out the corresponding tricritical line as a function of hop rate. An analysis is also provided of the tricritical “epidemic exponent” for the case of no hopping. The phase diagram is also recovered qualitatively by applying mean-field and pair-approximations to the exact hierarchical form of the master equation for these models.     

Anisotropic cosmological models with bulk viscosity and particle creation in Saez–Ballester theory of gravitation

The paper deals with the study of particle creation and bulk viscosity in the evolution of spatially homogeneous and anisotropic Bianchi type-V cosmological models in the framework of Saez–Ballester theory of gravitation. Particle creation and bulk viscosity are considered as separate irreversible processes. The energy–momentum tensor is modified to accommodate the viscous pressure and creation pressure which is associated with the creation of matter out of gravitational field. A special law of variation of Hubble parameter is applied to obtain exact solutions of field equations in two types of cosmologies, one with power-law expansion and the other with exponential expansion. Cosmological model with power-law expansion has a Big-Bang singularity at time t = 0, whereas the model with exponential expansion has no finite singularity. We study bulk viscosity and particle creation in each model in four different cases. The bulk viscosity coefficient is obtained for full causal, Eckart’s and truncated theories. All physical parameters are calculated and thoroughly discussed in both models.     

How Will a Particle Detector Respond in Massless Complex Scalar Field？

I study the response of a particle detector coupled to quantized massless complex scalar field in four dimensional Minkowski spacetime through nonlinear Lagrangian. I find that as in the real scalar field： the particle detector will not respond when it is in inertial motion; If accelerated in its own frame reference, it does respond and feel the same temperature. But different from the real scalar field case, the detector＇s transition amplitude is concerned with particle-antiparticle creation, and the response of the detector is （1/α^2 ＋ ε^2）/24π^2 times of that in real scalar field, with 1/α the accelerator of the detector and e the energy gap between the detector＇s two energy level. It is due to the nonlinear property of the coupling Lagrangian. Whether the total charge of the system constructed by the particle detector and vacuum is conserved is also considered and analyzed.     

Some remarks on spinor particle pair creation in alternating homogeneous external field

It is shown that the dynamical symmetry group of the problem of spinor particle pair creation in alternating homogeneous external field is the SO (5) group. The probability of pair creation is given by the modulus square of the matrix element of spinor representation of this group.