Lattice QCD-based equations of state at vanishing net-baryon density

We present realistic equations of state for QCD matter at vanishing net-baryon density which embed recent lattice QCD results at high temperatures combined with a hadron resonance gas model in the low-temperature, confined phase. In the latter, we allow an implementation of partial chemical equilibrium, in which particle ratios are fixed at the chemical freeze-out, so that a description closer to the experimental situation is possible. Given the present uncertainty in the determination of the chemical freeze-out temperature from first-principle lattice QCD calculations, we consider different values within the expected range. The corresponding equations of state can be applied in the hydrodynamic modeling of relativistic heavy-ion collisions at the LHC and at the highest RHIC beam energies. Suitable parametrizations of our results as functions of the energy density are also provided

Lattice QCD-based equations of state at vanishing net-baryon density

We construct a realistic equation of state for QCD matter at vanishing net-baryon density, which is based on recent lattice QCD results at high temperatures combined with a hadron resonance gas model in the low-temperature, confined phase. Partial chemical equilibrium, in which certain particle ratios are fixed at the chemical freeze-out, can be implemented, allowing a description closer to the experimental situation. Given the present uncertainty in the chemical freeze-out temperature, we consider different values within the expected range. The resulting equations of state can be applied in the hydrodynamic modeling of relativistic heavy-ion collisions at the LHC and at the highest RHIC beam energies. Suitable parametrizations of our results are provided

Determination of freeze-out conditions from fluctuation observables measured at RHIC

We extract chemical freeze-out conditions via a thermal model approach from fluctuation observables measured at RHIC and compare with results from lattice QCD and statistical hadronization model fits. The possible influence of additional critical and non-critical fluctuation sources not accounted for in our analysis is discussed

Parametrization for chemical freeze-out conditions from net-charge fluctuations measured at RHIC

We discuss details of our thermal model applied to extract chemical freeze-out conditions from fluctuations in the net-electric charge and net-proton number measured at RHIC. A parametrization for these conditions as a function of the beam energy is given

Antiproton fluxes from light neutralinos

We analyze how the measurements of the low-energy spectrum of cosmic antiprotons can provide information on relic neutralinos. The analysis is focused on the light neutralinos which emerge in supersymmetric schemes where gaugino-mass unification is not assumed. We determine which ranges of the astrophysical parameters already imply stringent constraints on the supersymmetric configurations and those ranges which make the antiproton flux sensitive to the primary component generated by the neutralino self-annihilation. Our results are derived from some general properties of the antiproton flux proved to be valid for a generic cold dark matter candidate

Species Doublers as Super Multiplet Partners in Lattice Supersymmetry

We propose a new lattice superfield formalism in momentum representation which accommodates species doublers of the lattice fermions and their bosonic counterparts as super multiplets. We explicitly show that one dimensional $N=2$ model with interactions has exact supersymmetry on the lattice for all super charges with lattice momentum. In coordinate representation the finite difference operator is made to satisfy Leibnitz rule by introducing a non local product, the "star" product, and the exact lattice supersymmetry is realized. Supersymmetric Ward identities are shown to be satisfied at one loop level

Angularities and other shapes

I discuss soft-gluon resummation and power corrections for event shape distributions, mostly in e+ e- annihilation. I consider specifically the thrust, the C parameter, and the class of angularities, and show how factorization techniques and dressed gluon exponentiation lead to predictive models of power corrections that are firmly grounded in perturbative QCD. The scaling rule for the shape function for angularities is derived as an example. Finally, I make a few remarks on possible generalizations to hadron collisions, and on their relevance to LHC studies

Theoretical issues at LEP2 and LC

After 12 years of glorious data taking LEP has been shut down. During the past two years an incredible effort has been devoted to get more accurate predictions and estimates of the related theoretical uncertainties. Many of the theoretical questions driven by LEP are also relevant at the LC, where predictions will be needed with even higher accuracy. This is particularly true for 4-fermion Physics. In this contribution, I review some of the most important theoretical achievements at LEP in understanding W and Z pair production, 4-fermion + 1 visible photon signatures and in solving problems related with gauge invariance. Issues on single W Physics are covered elsewhere. Part of the presented work is in progress, the final LEP2 analysis still being under way

Topics on four-fermion Physics at electron-positron colliders

I review the most recent progresses in the calculation of four-fermion processes in electron-positron collision

Are Constants Constant?

The prospect of a time-dependent Higgs vacuum expectation value is examined within the standard model of electroweak interactions. It is shown that the classical equation of motion for the Higgs field admits a solution that is a doubly-periodic function of time. The corresponding Dirac equation for the electron field is equivalent to a second order differential equation with doubly-periodic coefficients. In the limit of very large primitive period of the Higgs background this equation can be solved in WKBJ approximation, showing plane-wave solutions with a time-dependent distortion factor which can be made arbitrarily small