International Journal of Modern Physics A

We work out an effective theory of accelerated expansion for the background to describe general phenomena of inflation and acceleration (dark energy) in the universe. Our aim is to determine from theoretical grounds, in a physically motivated and model-independent way, which and how many (free) parameters are needed to broadly capture the physics of a theory describing the background of cosmic acceleration. Our goal is to make as much transparent as possible the physical interpretation of the parameters describing the expansion. We show that, at leading order, there are five independent parameters, of which one can be constrained via general relativity tests. The other four parameters need to be determined by observing and measuring the cosmic expansion rate only, H(z). Therefore, we suggest that future cosmology surveys focus on obtaining an accurate value as possible measurement of H(z) to constrain the nature of accelerated expansion.

Final results of a detailed analysis of p+p elastic scattering data are presented, utilizing the quark–diquark model of protons in a form proposed by Bialas and Bzdak. The differential cross-section of elastic proton–proton collisions is analyzed in a detailed and systematic manner at small momentum transfers, starting from the energy range of CERN ISR at , including also recent TOTEM data at the present LHC energies at . These studies confirm the picture that the size of proton increases systematically with increasing energies, while the size of the constituent quarks and diquarks remains approximately independent of (or only increases slightly with) the colliding energy. The detailed analysis indicates correlations between model parameters and also indicates an increasing role of shadowing at LHC energies. Within the investigated class of models, a simple and model-independent phenomenological relation was discovered that connects the total p+p scattering cross-section to the effective quark, diquark size and their average separation. Our best fits indicate that the relative error of this phenomenological relation is 10–15% in the considered energy range.

In this paper, we investigate the problem of fermion creation inside a three-dimensional cubic box. We present an appropriate wave function which satisfies the Dirac equation in this geometry with MIT bag model boundary condition. We consider the box with oscillating walls and introduce the time evolution of the quantized field by expanding it over the instantaneous basis. We explain how we can obtain the average number of particles created. In this regard, we find the Bogoliubov coefficients. We consider an oscillation and determine the coupling conditions between different modes that can be satisfied depending on the cavity's spectrum. Assuming the parametric resonance case we obtain an expression for the mean number of created fermions in each mode of an oscillation and their dynamical Casimir energy.

In this work, we investigate the quantum theory of light propagating in D-dimensional de Sitter space–times. To do so, we use the method of dynamic invariants to obtain the solution of the time-dependent Schrödinger equation. The quantum behavior of the electromagnetic field in this background is analyzed. As the electromagnetism loses its conformality in D≠4, we point out that there will be particle production and comoving objects will feel a Bunch–Davies thermal bath. This may become important in extra dimension physics and raises the intriguing possibility that precise measurements of the Cosmic Microwave Background could verify the existence of extra dimensions.

We derive cutting rules for loop integrals containing propagators with complex masses. Using a field-theoretical model of a heavy vector boson interacting with a light fermion, we demonstrate that the complex-mass scheme respects unitarity order by order in a perturbative expansion provided that the renormalized coupling constant remains real.

We consider the decay modes of the heavy bound states originating from Higgs boson exchange between quark–antiquark pair. In case of a small coupling between the fourth and lower generation the main decay mode is annihilation. We show that for a vector state the dominant decay modes are Higgs-gamma and Higgs-Z decays, while for a pseudoscalar state the strong two-gluon decay mode dominates. The bound states are very narrow. The ratio of the total width to the binding energy is less than 1% if we are not extremely close to the critical quark mass where the binding energy is very small. The discussed decay modes exist for any fermion–antifermion bound states including heavy leptons and heavy neutrinos if their masses are high enough to form a bound state due to attractive Higgs boson exchange potential.