Two-dimensional nonstationary model of the propagation of an electron beam in a vacuum

A two dimensional nonstationary model of the propagation of a relativistic electron beam injected into a vacuum is considered. Collision effects are ignored and there are no external fields. Two types of the electron current propagation are shown from the computer simulation of the Maxwell-Vlasov equations

On the origin of cosmic rays

Uniform and metagalactic cosmic ray models - halo, disk, and nonstationary galactic model

Finite-Size Effects in the ϕ4\phi^{4} Field Theory Above the Upper Critical Dimension

We demonstrate that the standard O(n) symmetric $\phi^{4}$ field theory does not correctly describe the leading finite-size effects near the critical point of spin systems on a $d$-dimensional lattice with $d > 4$. We show that these finite-size effects require a description in terms of a lattice Hamiltonian. For $n \to \infty$ and $n=1$ explicit results are given for the susceptibility and for the Binder cumulant. They imply that recent analyses of Monte-Carlo results for the five-dimensional Ising model are not conclusive.Comment: 4 pages, latex, 1 figur

On some problems of gamma-astronomy

Gamma ray emissions from young supernova remnants are discussed and calculated. The positron annihilation line is also calculated. Decay of charged pions in remnants cause generation of high energy neutrinos. This emission of neutrinos is reviewed. The CR origin and gamma emission from Magellanic clouds help to establish the intensity gradient in the galaxy. This gamma astronomical data is briefly discussed

Beam energy measurement at linear colliders using spin precession

Linear collider designs foresee some bends of about 5-10 mrad. The spin precession angle of one TeV electrons on 10 mrad bend is 23.2 rad and it changes proportional to the energy. Measurement of the spin direction using Compton scattering of laser light on electrons before and after the bend allows determining the beam energy with an accuracy about of 10^{-5}. In this paper the principle of the method, the procedure of the measurement and possible errors are discussed. Some remarks about importance of plasma focusing effects in the method of beam energy measurement using Moller scattering are given.Comment: 7 pages, Latex, 4 figures(.eps). In v.3 corresponds to journal publication. Talk at 26-th Advanced ICFA Beam Dynamic Workshop on Nanometre-Size Colliding Beams (Nanobeam2002), Lausanne, Switzerland, Sept 2-6, 200

The Q2Q^2 dependence of the hard diffractive photoproduction of vector meson or photon and the range of pQCD validity

We consider two coupled problems. We study the dependence on photon virtuality $Q^2$ for the semihard quasi--elastic photoproduction of neutral vector mesons on a quark, gluon or real photon (at $s\gg p_{\bot}^2,\;Q^2; \; p_{\bot}^2\gg \mu^2 \approx (0.3$ GeV)$^2$). To this end we calculate the corresponding amplitudes (in an analytical form) in the lowest nontrivial approximation of perturbative QCD. It is shown that the amplitude for the production of light meson varies very rapidly with the photon virtuality near $Q^2=0$. We estimate the bound of the pQCD validity region for such processes. For the real incident photon the obtained bound for the $\rho$ meson production is very high. This bound decreases fast with the increase of $Q^2$, and we expect that the virtual photoproduction at HERA gives opportunity to test the pQCD results. The signature of this region is discussed. For the hard Compton effect the pQCD should work good at not too high $p_{\bot}$, and this effect seems measurable at HERA.Comment: ReVTeX, 36 pages, 5 Postscript figures, uses epsf.st

High Energy Photon-Photon Collisions at a Linear Collider

High intensity back-scattered laser beams will allow the efficient conversion of a substantial fraction of the incident lepton energy into high energy photons, thus significantly extending the physics capabilities of an electron-electron or electron-positron linear collider. The annihilation of two photons produces C=+ final states in virtually all angular momentum states. The annihilation of polarized photons into the Higgs boson determines its fundamental two-photon coupling as well as determining its parity. Other novel two-photon processes include the two-photon production of charged lepton pairs, vector boson pairs, as well as supersymmetric squark and slepton pairs and Higgstrahlung. The one-loop box diagram leads to the production of pairs of neutral particles. High energy photon-photon collisions can also provide a remarkably background-free laboratory for studying possibly anomalous $W W$ collisions and annihilation. In the case of QCD, each photon can materialize as a quark anti-quark pair which interact via multiple gluon exchange. The diffractive channels in photon-photon collisions allow a novel look at the QCD pomeron and odderon. Odderon exchange can be identified by looking at the heavy quark asymmetry. In the case of electron-photon collisions, one can measure the photon structure functions and its various components. Exclusive hadron production processes in photon-photon collisions test QCD at the amplitude level and measure the hadron distribution amplitudes which control exclusive semi-leptonic and two-body hadronic B-decays.Comment: Invited talk, presented at the 5th International Workshop On Electron-Electron Interactions At TeV Energies, Santa Cruz, California, 12-14 December 200

Effective Potential for Scalar Field in Three Dimensions: Ising Model in the Ferromagnetic Phase

We compute the effective potential $V_{\rm eff}(\phi)$ for one-component real scalar field $\phi$ in three Euclidean dimensions (3D) in the case of spontaneously broken symmetry, from the Monte Carlo simulation of the 3D Ising model in external field at temperatures approaching the phase transition from below. We study probability distributions of the order parameter on the lattices from $30^3$ to $74^3$, at $L/\xi \approx 10$. We find that, in close analogy with the symmetric case, $\phi^6$ plays an important role: $V_{\rm eff}(\phi)$ is very well approximated by the sum of $\phi^2$, $\phi^4$ and $\phi^6$ terms. An unexpected feature is the negative sign of the $\phi^4$ term. As close to the continuum limit as we can get ($\xi \approx 7.2$), we obtain $${\cal L}_{\rm eff} \approx {1 \over 2} \partial_\mu \phi \partial_\mu \phi + 1.7 (\phi^2 - \eta^2)^2 (\phi^2 + \eta^2).$$ We also compute several universal coupling constants and ratios, including the combination of critical amplitudes $C^- (f_1^-)^{-3} B^{-2}$.Comment: 13 pages, 5 Postscript figures, uses epsf.st