Hubble Diagram of Gamma-Rays Bursts calibrated with Gurzadyan-Xue Cosmology

Gamma-ray bursts (GRBs) being the most luminous among known cosmic objects carry an essential potential for cosmological studies if properly used as standard candles. In this paper we test with GRBs the cosmological predictions of the Gurzadyan-Xue (GX) model of dark energy, a novel theory that predicts, without any free parameters, the current vacuum fluctuation energy density close to the value inferred from the SNIa observations. We also compare the GX results with those predicted by the concordance scenario $\Lambda$-CDM. According to the statistical approach by Schaefer (2007), the use of several empirical relations obtained from GRBs observables, after a consistent calibration for a specific model, enables one to probe current cosmological models. Based on this recently introduced method, we use the 69 GRBs sample collected by Schaefer (2007); and the most recently released SWIFT satellite data (Sakamoto et al. 2007) together with the 41 GRBs sample collected by Rizzuto et al. (2007), which has the more firmly determined redshifts. Both data samples span a distance scale up to redshift about 7. We show that the GX models are compatible with the Hubble diagram of the Schaefer (2007) 69 GRBs sample. Such adjustment is almost identical to the one for the concordance $\Lambda$-CDM.Comment: 9 pages, 17 figures, 11 tables; Astr. & Astrophys. (in press

Magnetic Field of Relativistic Nonlinear Plasma Wave

Longitudinal and transverse behavior of magnetic field of relativistic nonlinear three-dimensional plasma wave is investigated. It is shown that the magnetic field of the wave is different from zero and performs higher frequency oscillations compared to the plasma electron frequency. An increase in the nonlinearity leads to strengthening of magnetic field. The oscillations of magnetic field in transverse direction arise, that caused by the phase front curving of nonlinear plasma wave. The numerical results well conform with predictions of the analytical consideration of weakly-nonlinear case.Comment: 6 pages, 3 figure

Excitation of nonlinear two-dimensional wake waves in radially-nonuniform plasma

It is shown that an undesirable curvature of the wave front of two-dimensional nonlinear wake wave excited in uniform plasma by a relativistic charged bunch or laser pulse may be compensated by radial change of the equilibrium plasma density.Comment: 6 pages, 4 figure

On the possibility of q-scaling in high energy production processes

It has been noticed recently that transverse momenta (p_T) distributions observed in high energy production processes exhibit remarkably universal scaling behaviour. This is the case when a suitable variable replaces the usual p_T. On the other hand, it is also widely known that transverse momentum distributions in general follow a power-like Tsallis distribution, rather than an exponential Boltzmann-Gibbs, with a (generally energy dependent) nonextensivity parameter q. Here we show that it is possible to choose a suitable variable such that all the data can be fitted by the same Tsallis distribution (with the same, energy independent value of the q-parameter). Thus they exhibit q-scaling.Comment: Final version, accepted by J.Phys.

A Rationale for Long-lived Quarks and Leptons at the LHC: Low Energy Flavour Theory

In the framework of gauged flavour symmetries, new fermions in parity symmetric representations of the standard model are generically needed for the compensation of mixed anomalies. The key point is that their masses are also protected by flavour symmetries and some of them are expected to lie way below the flavour symmetry breaking scale(s), which has to occur many orders of magnitude above the electroweak scale to be compatible with the available data from flavour changing neutral currents and CP violation experiments. We argue that, actually, some of these fermions would plausibly get masses within the LHC range. If they are taken to be heavy quarks and leptons, in (bi)-fundamental representations of the standard model symmetries, their mixings with the light ones are strongly constrained to be very small by electroweak precision data. The alternative chosen here is to exactly forbid such mixings by breaking of flavour symmetries into an exact discrete symmetry, the so-called proton-hexality, primarily suggested to avoid proton decay. As a consequence of the large value needed for the flavour breaking scale, those heavy particles are long-lived and rather appropriate for the current and future searches at the LHC for quasi-stable hadrons and leptons. In fact, the LHC experiments have already started to look for them.Comment: 10 pages, 1 figur

The Tsallis Distribution in Proton-Proton Collisions at s\sqrt{s} = 0.9 TeV at the LHC

The Tsallis distribution has been used recently to fit the transverse momentum distributions of identified particles by the STAR and PHENIX collaborations at the Relativistic Heavy Ion Collider and by the ALICE and CMS collaborations at the Large Hadron Collider. Theoretical issues are clarified concerning the thermodynamic consistency of the Tsallis distribution in the particular case of relativistic high energy quantum distributions. An improved form is proposed for describing the transverse momentum distribution and fits are presented together with estimates of the parameter $q$ and the temperature $T$.Comment: 15 pages, 7 figures. arXiv admin note: substantial text overlap with arXiv:1106.340

Theoretical predictions for charm and bottom production at the LHC

We present predictions for a variety of single-inclusive observables that stem from the production of charm and bottom quark pairs at the 7 TeV LHC. They are obtained within the FONLL semi-analytical framework, and with two "Monte Carlo + NLO" approaches, MC@NLO and POWHEG. Results are given for final states and acceptance cuts that are as close as possible to those used by experimental collaborations and, where feasible, are compared to LHC data.Comment: 22 pages, 10 figure

Colour reconnections in Herwig++

We describe the implementation details of the colour reconnection model in the event generator Herwig++. We study the impact on final-state observables in detail and confirm the model idea from colour preconfinement on the basis of studies within the cluster hadronization model. Moreover, we show that the description of minimum bias and underlying event data at the LHC is improved with this model and present results of a tune to available data.Comment: 19 pages, 21 figures, 2 tables. Matches with published versio

Gauged flavour symmetry for the light generations

We study the phenomenology of a model where an SU(2)^3 flavour symmetry acting on the first two generation quarks is gauged and Yukawa couplings for the light generations are generated by a see-saw mechanism involving heavy fermions needed to cancel flavour-gauge anomalies. We find that, in constrast to the SU(3)^3 case studied in the literature, most of the constraints related to the third generation, like electroweak precision bounds or B physics observables, can be evaded, while characteristic collider signatures are predicted.Comment: 16 pages, 3 figure

An Integrable Model with non-reducible three particle R-Matrix

We define an integrable lattice model which, in the notation of Yang, in addition to the conventional 2-particle $R$-matrices also contains non-reducible 3-particle $R$-matrices. The corresponding modified Yang-Baxter equations are solved and an expression for the transfer matrix is found as a normal ordered exponential of a (non-local) Hamiltonian.Comment: 13 pages, 4 figure