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Search Results: 1 - 10 of 463450 matches for " A. Mueller "
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Parton Saturation at Small x and in Large Nuclei
A. H. Mueller
Physics , 1999, DOI: 10.1016/S0550-3213(99)00394-6
Abstract: Quark and gluon distributions in the light-cone wavefunction of a high energy hadron or nucleus are calculated in the saturation regime. One loop calculations are performed explicitly using the equivalence between the parton distribution in the light-cone wavefunction and the production distribution of that parton in a current-nucleon (nucleus) scattering. We argue that, except for some overall numerical factors, the Weizsacker- Williams wavefunction correctly gives the physics of the gluon distribution in a light-cone wavefunction.
Limitations on using the operator product expansion at small values of x
A. H. Mueller
Physics , 1996, DOI: 10.1016/S0370-2693(97)00116-0
Abstract: Limits on the regions of $Q^2$ and x where the operator product expansion canbe safely used, at small values of x are given. For a fixed large $Q^2$ there is an $x_0(Q^2)$ such that for Bjorken x-values below $x_0$ the operator product expansion breaks down with significant nonperturbative corrections occurring in the leading twist coefficient and anomlous dimension functions due to diffusion of gluons to small values of transverse momentum.
Diffusive spin transport
Cord A. Mueller
Physics , 2007, DOI: 10.1007/978-3-540-88169-8_6
Abstract: Information to be stored and transported requires physical carriers. The quantum bit of information (qubit) can for instance be realised as the spin 1/2 degree of freedom of a massive particle like an electron or as the spin 1 polarisation of a massless photon. In this lecture, I first use irreducible representations of the rotation group to characterise the spin dynamics in a least redundant manner. Specifically, I describe the decoherence dynamics of an arbitrary spin S coupled to a randomly fluctuating magnetic field in the Liouville space formalism. Secondly, I discuss the diffusive dynamics of the particle's position in space due to the presence of randomly placed impurities. Combining these two dynamics yields a coherent, unified picture of diffusive spin transport, as applicable to mesoscopic electronic devices or photons propagating in cold atomic clouds.
General Issues in Small-x and Diffractive Physics
A. H. Mueller
Physics , 1997, DOI: 10.1007/s100500050027
Abstract: A selected review of topics at the border of hard and soft physics is given. Particular emphasis is a placed on diffraction dissociation at Fermilab and HERA. Recently, significant differences between diffraction dissociation at HERA and at Fermilab have become apparent. This may suggest that one already is reaching nonlinear (unitarity) effects which are extending from the soft physics region into the semihard regime of QCD.
The Boltzmann equation for gluons at early times after a heavy ion collision
A. H. Mueller
Physics , 1999, DOI: 10.1016/S0370-2693(00)00084-8
Abstract: A Boltzmann equation is given for the early stages of evolution of the gluon system produced in a head-on collision. The collision term is taken from gluon- gluon approximation. < p_\perp > and < p_z^2 > are evaluated as a function of time using initial conditions taken from the McLerran-Venugopalan model.
The locality of the square-root method for improved staggered quarks
A. Hart,E. Mueller
Physics , 2004, DOI: 10.1103/PhysRevD.70.057502
Abstract: We study the effects of improvement on the locality of square-rooted staggered Dirac operators in lattice QCD simulations. We find the localisation lengths of the improved operators (FAT7TAD and ASQTAD) to be very similar to that of the one-link operator studied by Bunk et al., being at least the Compton wavelength of the lightest particle in the theory, even in the continuum limit. We conclude that improvement has no effect. We discuss the implications of this result for the locality of the nth-rooted fermion determinant used to reduce the number of sea quark flavours, and for possible staggered valence quark formulations.
QCD and Nuclear Physics
A. H. Mueller
Physics , 1999, DOI: 10.1016/S0375-9474(99)00246-8
Abstract: The main part of this talk is a review and summary of how QCD is used in two main areas of nuclear physics, namely in determining the quark flavor and spin content of the proton and in ultrarelativistic heavy ion collisions. Brief comments are made concerning effective theories in hadron physics and on the separation of various twists in using the operator product expansion to analyze hard processes.
Localization of solitons: linear response of the mean-field ground state to weak external potentials
Cord A. Mueller
Physics , 2010, DOI: 10.1007/s00340-011-4425-3
Abstract: Two aspects of bright matter-wave solitons in weak external potentials are discussed. First, we briefly review recent results on the Anderson localization of an entire soliton in disordered potentials [Sacha et al. PRL 103, 210402 (2009)], as a paradigmatic showcase of genuine quantum dynamics beyond simple perturbation theory. Second, we calculate the linear response of the mean-field soliton shape to a weak, but otherwise arbitrary external potential, with a detailed application to lattice potentials.
A Simple Derivation of the JIMWLK Equation
A. H. Mueller
Physics , 2001, DOI: 10.1016/S0370-2693(01)01343-0
Abstract: A simple derivation of the Jalilian-Marian, Iancu, McLerran, Weigert, Leonidov and Kovner (JIMWLK) equation for the evolution of small-x QCD wavefunctions is given. The derivation makes use of the equivalence between the evolution of a (in general complicated) small-x wavefunction with that of the evolution of the (simple) dipole probing the wavefunction in a high energy scattering.
Toward Equilibration in the Early Stages After a High Energy Heavy Ion Collision
A. H. Mueller
Physics , 1999, DOI: 10.1016/S0550-3213(99)00502-7
Abstract: The early stages in the evolution of the gluons produced in the central region of a head-on high-energy heavy ion collision is studied. An equation is given for the rate of change of transverse momentum into longitudinal momentum where the longitudinal direction is along the collision axis. We are able to follow the system up to the time where equilibration seems to be setting in, but we are unable to actually follow the system as it reaches equilibrium.
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