875394
phi4 model near the critical point: The Gaussian variational approximation.
Using the Gaussian variational approximation, we describe the approach to the continuum limit in φ 4 theory in 3+1 space-time dimensions. We study the solutions of the variational equations and their stability and compare our results with those of Monte Carlo calculations on a lattice. The importance of lattice effects is investigated by putting the Gaussian wave functional on a lattice. We find an abrupt decrease of the fourth derivative of the effective potential in the vicinity of the critical point, which is consistent with Monte Carlo calculations. In the continuum limit b→0 + , the renormalized theory shows a broken phase which is found to be asymptotically free, in agreement with the conclusions of Branchina et al
16683941
Ground state properties and glueball spectrum in SU(2) Yang-Mills theory using gauge invariant variables
We describe a nonperturbative calculation of the spectrum of SU(2) Yang-Mills theory based on a Hamiltonian formulation. Our approach exploits gauge invariant variables similar to those used in nuclear physics to describe collective motion in nuclei.
33800044
Finite-size and dynamical effects in pair production by an external field.
We evaluate the rate of pair production in a uniform electric field confined to a bounded region in space. Using the Balian-Bloch expansion of Green's functions we obtain explicit expressions for finite-size corrections to Schwinger's formula. The case of a time-dependent boundary, relevant to describe energy deposition by quark-antiquark pair production in ultrarelativistic collisions, is also investigated. We find that finite-size effects are important in nuclear collisions. They decrease when the strength of the chromoelectric field between the nuclei is large. As a result, the rate of energy deposition increases sharply with the mass number {ital A} of the colliding nuclei.
17246313
Variational Approximations for Correlation Functions in Quantum Field Theories
Abstract Applying the time-dependent variational principle of Balian and Veneroni, we derive variational approximations for multi-time correlation functions in Φ 4 field theory. We assume first that the initial state is given and characterized by a density operator equal to a Gaussian density matrix. Then, we study the more realistic situation where only a few expectation values are given at the initial time and we perform an optimization with respect to the initial state. We calculate explicitly the two-time correlation functions with two and four field operators at equilibrium in the symmetric phase.
8691879
Gauge Invariant Variables for SU ( 2 ) Yang-Mills Theory
We describe a nonperturbative calculation of the spectrum of SU(2) Yang-Mills theory based on a Hamiltonian formulation. Our approach exploits gauge invariant variables similar to those used in nuclear physics to describe collective motion in nuclei.
17341915
Self similar solutions of the evolution equation of a scalar field in an expanding geometry
Abstract We consider the functional Schrodinger equation for a self interacting scalar field in an expanding geometry. By performing a time dependent scale transformation on the argument of the field we derive a functional Schrodinger equation whose hamiltonian is time independent but involves a time-odd term associated to a constraint on the expansion current. We study the mean field approximation to this equation and generalize in this case for interacting fields, the solutions worked out by Bunch and Davies for free fields.
31666144
Testing the single-quark radiation hypothesis.
In the quark model, radiative transitions between hadronic states are assumed to involve a single quark and not the hadron as a whole. We describe a possible test of this hypothesis using $p\overline{p}\ensuremath{\rightarrow}{\ensuremath{\chi}}_{2}\ensuremath{\rightarrow}\ensuremath{\psi}\ensuremath{\gamma}$ with $\ensuremath{\psi}\ensuremath{\rightarrow}{e}^{+}{e}^{\ensuremath{-}}$.
10342426
Physically meaningful and not so meaningful symmetries in Chern-Simons theory.
We explicitly show that the Landau gauge supersymmetry of Chern-Simons theory does not have any physical significance. In fact, the difference between an effective action that is both Becchi-Rouet-Stora (BRS) invariant and Landau supersymmetric and an effective action that is only BRS invariant is a finite field redefinition. Having established this, we use a BRS-invariant regulator that defines CS theory as the large mass limit of topologically massive Yang-Mills theory to discuss the shift [ital k][r arrow][ital k]+[ital c][sub [ital V]] of the bare Chern-Simons parameter [ital k] in connection with the Landau supersymmetry. Finally, to convince ourselves that the shift above is not an accident of our regularization method, we comment on the fact that all BRS-invariant regulators used as yet yield the same value for the shift.
18738644
Observable jets from the BFKL chain.
We derive a modified form of the BFKL equation which enables the structure of the gluon emissions to be studied in small {ital x} deep-inelastic scattering. The equation incorporates the resummation of the virtual and unresolved real gluon emissions. We solve the equation to calculate the number of small {ital x} deep-inelastic events containing 0,1,2,... resolved gluon jets, that is, jets with transverse momenta {ital q}{sub {ital T}}{gt}{mu}. We study the jet decomposition for different choices of the jet resolution parameter {mu}. {copyright} {ital 1996 The American Physical Society.}
28650811
Crossing intrinsic depolarizing resonances by varying a partial Siberian snake.
We recently forced a 140 MeV polarized proton beam to cross intrinsic depolarizing resonances by varying a partial Siberian snake{close_quote}s strength for different values of the vertical and horizontal betatron tunes {nu}{sub {ital y}} and {nu}{sub {ital x}}. A weak second-order intrinsic resonance was observed in the {nu}{sub {ital x}} sweep; moreover, an unexpected partial spin flip was found in the {nu}{sub {ital y}} sweep. We also varied the snake ramp time to identify the {nu}{sub {ital y}} and {nu}{sub {ital x}} regions where the resonance crossings occurred during the snake variation; in these crossings the polarization partially deviated from Froissart-Stora behavior. {copyright} {ital 1996 The American Physical Society.}
28053143
Renormalizable top-quark condensate models.
Recently it has been suggested that electroweak symmetry is broken by a top-quark vacuum condensate. We discuss the prospects for making a renormalizable version of this ``top bootstrap'' scenario using a strongly coupled spontaneously broken gauge interaction. Several specific models are considered. We argue that these models are somewhat similar to the extended technicolor models, but with a ``technicolor'' force which is broken, providing the mass-generation mechanism for the top quark. From this point of view, the top quark plays the role of a techniquark.