A study of the impact of the Ceramic Materials Research program at the University of Washington Final report, 15 Jun. 1968 - 15 Sep. 1969

Impact of Ceramic Materials Research Program at University of Washingto

Photoinjector-generation of a flat electron beam with transverse emittance ratio of 100

The generation of a flat electron beam directly from a photoinjector is an attractive alternative to the electron damping ring as envisioned for linear colliders. It also has potential applications to light sources such as the generation of ultra-short x-ray pulses or Smith-Purcell free electron lasers. In this Letter, we report on the experimental generation of a flat-beam with a measured transverse emittance ratio of $100\pm 20.2$ for a bunch charge of $\sim 0.5$ nC; the smaller measured normalized root-mean-square emittance is $\sim 0.4$ $\mu$m and is limited by the resolution of our experimental setup. The experimental data, obtained at the Fermilab/NICADD Photoinjector Laboratory, are compared with numerical simulations and the expected scaling laws.Comment: 5 pages, 3 figure

On the Theory of Relativistic Strong Plasma Waves

The influence of motion of ions and electron temperature on nonlinear one-dimensional plasma waves with velocity close to the speed of light in vacuum is investigated. It is shown that although the wavebreaking field weakly depends on mass of ions, the nonlinear relativistic wavelength essentially changes. The nonlinearity leads to the increase of the strong plasma wavelength, while the motion of ions leads to the decrease of the wavelength. Both hydrodynamic approach and kinetic one, based on Vlasov-Poisson equations, are used to investigate the relativistic strong plasma waves in a warm plasma. The existence of relativistic solitons in a thermal plasma is predicted.Comment: 13 pages, 8 figure

Stability of the Black Hole Horizon and the Landau Ghost

The stability of the black hole horizon is demanded by both cosmic censorship and the generalized second law of thermodynamics. We test the consistency of these principles by attempting to exceed the black hole extremality condition in various process in which a U(1) charge is added to a nearly extreme Reissner--Nordstr\"om black hole charged with a {\it different\/} type of U(1) charge. For an infalling spherical charged shell the attempt is foiled by the self--Coulomb repulsion of the shell. For an infalling classical charge it fails because the required classical charge radius exceeds the size of the black hole. For a quantum charge the horizon is saved because in order to avoid the Landau ghost, the effective coupling constant cannot be large enough to accomplish the removal.Comment: 12 pages, RevTe

Witten-Veneziano from Green-Schwarz

We consider the U(1) problem within the AdS/CFT framework. We explain how the Witten-Veneziano formula for the eta' mass is related to a generalized Green-Schwarz mechanism. The closed string mode, that cancels the anomaly of the gauged U(1) axial symmetry, is identified with the eta' meson. In a particular set-up of D3-branes on a C3/(Z3xZ3) orbifold singularity, the eta' meson is a twisted-sector R-R field.Comment: 10 pages, LaTex. 1 eps figure. v2: minor changes, refs. added, to appear in JHE

Non-universality of compact support probability distributions in random matrix theory

The two-point resolvent is calculated in the large-n limit for the generalized fixed and bounded trace ensembles. It is shown to disagree with that of the canonical Gaussian ensemble by a nonuniversal part that is given explicitly for all monomial potentials V(M)=M2p. Moreover, we prove that for the generalized fixed and bounded trace ensemble all k-point resolvents agree in the large-n limit, despite their nonuniversality

Probing Gauge String Formation in a Superconducting Phase Transition

Superconductors are the only experimentally accessible systems with spontaneously broken gauge symmetries which support topologically nontrivial defects, namely string defects. We propose two experiments whose aim is the observation of the dense network of these strings thought to arise, via the Kibble mechanism, in the course of a spontaneous symmetry breaking phase transition. We suggest ways to estimate the order of magnitude of the density of flux tubes produced in the phase transition. This may provide an experimental check for the theories of the production of topological defects in a spontaneously broken gauge theory, such as those employed in the context of the early Universe.Comment: 16 pages (Latex), 4 figures included, change in title, some minor changes, published versio

Semiclassical Decay of Excited String States on Leading Regge Trajectories

We study the decay of hadrons based on a semiclassical string model. By including quark mass effects we find that the width to mass ratio \G/m is an increasing function of $m$, which increases most rapidly for massive quarks. This is consistent with the available data. The decay probability of hadrons on the leading Regge trajectories is computed taking the effect of the string rotation into account. The resulting decay probability is no longer uniform along the length of the string but varies in a manner that is in qualitative agreement with the available data. We argue in favour of possible experiments that would test our predictions more accurately and help open a window to the nonperturbative aspects of QCD.Comment: 15 PAGES, UR-1326, ER-40685-776, SU-4240-55

Observation of Plasma Focusing of a 28.5 GeV Positron Beam

The observation of plasma focusing of a 28.5 GeV positron beam is reported. The plasma was formed by ionizing a nitrogen jet only 3 mm thick. Simultaneous focusing in both transverse dimensions was observed with effective focusing strengths of order Tesla per micron. The minimum area of the beam spot was reduced by a factor of 2.0 +/- 0.3 by the plasma. The longitudinal beam envelope was measured and compared with numerical calculations