Modern Physics Letters A

The basis of renormalon calculus is briefly discussed. This method is applied to study the QCD predictions for three different sum rules of deep-inelastic scattering, namely for the Gross–Llewellyn Smith, Bjorken polarized and unpolarized sum rules. It is shown that the renormalon structures of these a posteriori different physical quantities are closely related. These properties give us the hint that theoretical expressions of these three sum rules are similar both in the perturbative and nonperturbative sectors. Some phenomenological consequences of the new relations are discussed.

We explore the consequences of time-space noncommutativity in the quantum mechanics of atoms and molecules, focusing on the Moyal plane with just time-space noncommutativity . Space rotations and parity are not automorphisms of this algebra and are not symmetries of quantum physics. Still, when there are spectral degeneracies of a time-independent Hamiltonian on a commutative spacetime which are due to symmetries, they persist when θ_0i≠0: they do not depend at all on θ_0i. They give no clue about rotation and parity violation when θ_0i≠0. The persistence of degeneracies for θ_0i≠0 can be understood in terms of invariance under deformed noncommutative "rotations" and "parity". They are not spatial rotations and reflection. We explain such deformed symmetries. We emphasize the significance of time-dependent perturbations (for example, due to time-dependent electromagnetic fields) to observe noncommutativity. The formalism for treating transition processes is illustrated by the example of nonrelativistic hydrogen atom interacting with quantized electromagnetic field. In the tree approximation, the 2s→1s + γ transition for hydrogen is zero in the commutative case. As an example, we show that it is zero in the same approximation for θ_0i≠0. The importance of the deformed rotational symmetry is commented upon further using the decay Z⁰→2γ as an example.

We introduce the cosmic holographic bounds with two uv and ir cutoff scales, to deal with both the inflationary universe in the past and dark energy in the future. To describe quantum fluctuations of inflation on sub-horizon scales, we use the Bekenstein–Hawking energy bound. The Hubble bounds are introduced for classical fluctuations of inflation on super-horizon scales. It turns out that the Hubble entropy bound is satisfied with the entanglement entropy and the Hubble temperature bound leads to a condition for the slow-roll inflation. In order to describe the dark energy, we introduce the holographic energy density which is the one saturating the Bekenstein–Hawking energy bound for a weakly gravitating system. Here the uv (ir) cutoff is given by the Planck scale (future event horizon), respectively. As a result, we find the close connection between inflation and dark energy.

The medium-induced modifications of the π⁺π^- and annihilation mechanisms of dilepton production during relativistic heavy-ion collisions are considered in the frame of a specific model. The main assumption of the model: the pions (quarks) produced during a collision are effectively confined to a finite volume due to the dense hadron environment, in which they live for a finite time scaled as the lifetime of a fireball. The effect of the contraction of the phase space of the annihilating pion (quark) states on dilepton spectra is analyzed.

The end of a thermal inflation era, driven by the rolling of a flaton field coupled to the curvaton, cause a huge increase in the curvaton mass and decay rate while the curvaton is still frozen. It is shown that, if this increase is enough for the curvaton to immediately decay, low scale inflation with Hubble parameter H_* ~ 10³GeV is achieved for more natural values of the flaton-curvaton coupling constant λ (10^-10≲λ≲ 10^-4) and the curvaton bare mass m_σ (m_σ ≲ 1 GeV).

We implement the transition from dark matter to dark energy in k-essence cosmologies for a very large set of kinetic functions F, in a way alternative to recent proposals which use generalized Chaplygin gas and transient models. Here we require that the pressure admits a power-law expansion around some value of the kinetic energy where the pressure vanishes. In addition, for suitable values of the parameters of the model, the speed of sound of the dark matter will be low. We first present the discussion in fairly general terms, and later consider for illustration two examples.

The rise-up in boron neutrino spectrum at low energies has been studied within the framework of "pure LMA" scenario. Indirect bounds on the spectral "upturn" have been obtained from the available solar neutrino data. These bounds have been used to demonstrate the efficacy of the precision measurements of the "upturn" for further constraining the neutrino parameter space allowed by SNO salt phase data. The sterile neutrino flux has been constrained in the light of the recent 766.3 Ty KamLAND spectral data.

In this paper, the mechanical systems with fractional derivatives are studied by using Riewe's formalism. The path integral quantization of these systems is constructed as an integration over the canonical phase space coordinated. An example is shown.