By solving the Fokker-Planck equation directly we examine the effects of annihilation, particle escape and injection on the form of a steady-state positron distribution in thermal hydrogen plasmas with kT < mec. The positron fraction considered is small enough, so it does not affect the electron distribution which remains Maxwellian. We show that the escape of positrons in the form of electron-...

In a large region of the supersymmetry parameter space, the annihilation cross section for neutralino dark matter is strongly dependent on the relative velocity of the incoming particles. We explore the consequences of this velocity dependence in the context of indirect detection of dark matter from the galactic center. We find that the increase in the annihilation cross section at high velocit...

We calculate the cross section for s-wave neutralino annihilation to three-body final states below the WW and tt̄ thresholds. Such three-body channels may dominate the annihilation cross section if the neutralino mass is not too much less than mt and mW respectively. Furthermore, because neutrinos produced in these channels are much more energetic than those from the bb̄ or ττ channels, they can ...

The production and annihilation of antiprotons in the hadronic phase of heavy-ion collisions is evaluated within a thermal equilibrium approach. It is shown that the inverse reaction of pp̄ annihilation (i.e., multi-pion annihilation Nππ → pp̄ with Nπ ≃ 5-7) in connection with oversaturation of pion phase space (i.e., finite pion chemical potentials) plays an important role in understanding the o...

In this note D9and anti-D9-brane annihilation in type I string theory is probed by a D1-brane. We consider the covariant Green-Schwarz or twistor formulation of the probe theory. We expect the theory to be κ-invariant after the annihilation is completed. Conditions of the κ-invariance of the theory impose constraints on the background tachyon field. Solutions to the constraints define tachyon v...

The Galactic positrons, as observed by their annihilation gamma-ray line at 0.511 MeV, are difficult to account for with astrophysical sources. It has been proposed that they are produced instead by dark matter annihilation or decay in the inner Galactic halo. To avoid other constraints, these processes are required to occur "invisibly," such that the eventual positron annihilation is the only ...

Nanoparticles embedded in a matrix can trap positrons under certain conditions. In such cases nanoparticles can be effectively studied by means of positron annihilation because positron annihilation characteristics contain information related to nanoparticles’ electronic and atomic structure. Of great importance is to calculate the positron response from such nanoparticles. Then, nanoparticles ...

The annihilation rate of weakly interacting cold dark matter particles at the galactic center could be greatly enhanced by the growth of a density spike around the central supermassive black hole (SBH). Here we discuss the effects of hierarchical mergers on the central spike. Mergers between halos containing SBHs lead to the formation of SBH binaries which transfer energy to the dark matter par...

The order and the nature of the finite-temperature phase transition of QCD with two flavors of dynamical quarks is investigated. An analysis of the critical exponent of the specific heat is performed through finite-size and finite-mass scaling of various susceptibilities. Dual superconductivity of QCD vacuum is investigated using a disorder parameter, namely the v.e.v. of a monopole creation op...

In this paper all deformations of the general linear group, subject to certain restrictions which in particular ensure a smooth passage to the Lie group limit, are obtained. Representations are given in terms of certains sets of creation and annihilation operators. These creation and annihilation operators may belong to a generalisation of the q-quark type or q-hadronic type, of q-boson or q-fe...