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Full-Text Articles in Physics

Renormalization Of The Energy-Momentum Tensor And The Validity Of The Equivalence Principle At Finite Temperature, Jf Donoghue, Br Holstein, Rw Robinett Dec 1984

Renormalization Of The Energy-Momentum Tensor And The Validity Of The Equivalence Principle At Finite Temperature, Jf Donoghue, Br Holstein, Rw Robinett

Barry R Holstein

Using the techniques of finite-temperature field theory we renormalize the electromagnetic and gravitational couplings of an electron which is immersed in a heat bath with T


Comment On Aproaches To The Tricritical Point In Quasibinary Liquid Mixtures, Miron Kaufman, Robert B. Griffiths Aug 1984

Comment On Aproaches To The Tricritical Point In Quasibinary Liquid Mixtures, Miron Kaufman, Robert B. Griffiths

Miron Kaufman

No abstract provided.


Pseudodimensional Variation And Tricriticality Of Potts Models By Hierarchical Breaking Of Translational Invariance, Miron Kaufman, Mehran Kardar Jul 1984

Pseudodimensional Variation And Tricriticality Of Potts Models By Hierarchical Breaking Of Translational Invariance, Miron Kaufman, Mehran Kardar

Miron Kaufman

Potts models with equivalent- and nearest-neighbor interactions are solved exactly on Cayley trees. A parameter D is identified that plays a role similar to the spatial dimension on Bravais lattices. Breaking translational symmetry by the Cayley-tree hierarchy reduces D, leading to a changeover in the order of the phase transition via a novel tricritical point.


Guage Invariant De Gennes Model, Anthony Day, T. Lubensky Jun 1984

Guage Invariant De Gennes Model, Anthony Day, T. Lubensky

Anthony Roy Day

A gauge-invariant formulation of the de Gennes model for the nematic—to—smectic-A transition is presented. In this formulation the energy associated with the gauge field A⃗ reduces to the Frank elastic energy with the application of the constraint n⃗0·A⃗=0 where n⃗0 is the uniform equilibrium director and A⃗ is to be identified with deviations δn⃗ of the director from equilibrium. It is shown that thermodynamic quantities and renormalization-group recursion relations are gauge invariant. All gauge dependence appears in the exponent η describing order-parameter correlations. The gauge invariance of a negative dielectric anisotropy smectic-A in an ...


Spin Systems On Hierarchical Lattices. Ii. Some Examples Of Soluble Models, Miron Kaufman, Robert B. Griffiths Jun 1984

Spin Systems On Hierarchical Lattices. Ii. Some Examples Of Soluble Models, Miron Kaufman, Robert B. Griffiths

Miron Kaufman

Several examples are given of soluble models of phase-transition phenomena utilizing classical discrete spin systems with nearest-neighbor interaction on hierarchical lattices. These include critical exponents which depend continuously on a parameter, the Potts model on a lattice with two different coupling constants, surface tension, and excess free energy of a line of defects. In each case we point out similarities and differences with a corresponding Bravais-lattice model.


Duality And Potts Critical Amplitudes On A Class Of Hierarchical Lattices, Miron Kaufman Jun 1984

Duality And Potts Critical Amplitudes On A Class Of Hierarchical Lattices, Miron Kaufman

Miron Kaufman

By using the duality transformation on a class of hierarchical lattices, I show that the Potts critical amplitudes above and below the critical temperature are equal. Logarithmic modifications of the power-law singularity occur when the exponent 2—alpha is an even integer, but do not occur when 2—alpha equals an odd integer.


Short-Range And Infinite-Range Bond Percolation, Miron Kaufman, Mehran Kardar Apr 1984

Short-Range And Infinite-Range Bond Percolation, Miron Kaufman, Mehran Kardar

Miron Kaufman

A method for generalizing bond-percolation problems to include the possibility of infinite-range (equivalent-neighbor) bonds is presented. On Bravais lattices the crossover from nonclassical to classical (mean-field) percolation criticality in the presence of such bonds is described. The Cayley tree with nearest-neighbor and equivalent-neighbor bonds is solved exactly, and a nonuniversal line of percolation transitions with exponents dependent on nearest-neighbor bond occupation probability is observed. Points of logarithmic and exponential singularity are also encountered, and the behavior is interpreted as dimensional reduction due to the breaking of translational invariance by bonds of Cayley-tree connectivity.


Critical Amplitude Of The Potts Model: Zeroes And Divergences, Miron Kaufman, David Andelman Mar 1984

Critical Amplitude Of The Potts Model: Zeroes And Divergences, Miron Kaufman, David Andelman

Miron Kaufman

The critical amplitude of the q-state Potts-model free energy is studied as a function of q in two dimensions and on the diamond hierarchical lattice. The amplitude diverges at an infinite number of q values, qn,introducing logarithmic terms in the free energy. We expect that in each interval (qn,qn+1) there is a q value where the amplitude vanishes, affecting the singularity of the free energy as a function of temperature. Possible consequences for gelation and vulcanization of polymers are discussed.


Comment On Criticality Of The Anisotropic Quantum Heisenberg Model On A Self-Dual Hierarchical Lattice, Miron Kaufman, Mehran Kardar Feb 1984

Comment On Criticality Of The Anisotropic Quantum Heisenberg Model On A Self-Dual Hierarchical Lattice, Miron Kaufman, Mehran Kardar

Miron Kaufman

No abstract provided.


Realizable Renormalization Group And Finite-Size Scaling, Miron Kaufman, K. K. Mon Jan 1984

Realizable Renormalization Group And Finite-Size Scaling, Miron Kaufman, K. K. Mon

Miron Kaufman

We propose a sequence of renormalization-group transformations which are exact on hierarchical lattices and we argue, by employing finite-size scaling, that the corresponding sequence of critical exponents converges towards the exact values associated with a Bravais lattice. A test of this method is also presented.


Possibilities For Finite Grand Unification With N = 2 Supersymmetry, Asim Gangopadhyaya Dec 1983

Possibilities For Finite Grand Unification With N = 2 Supersymmetry, Asim Gangopadhyaya

Asim Gangopadhyaya

We study the prospects for constructing finite grand unified theories using softly broken N = 2 global supersymmetry. The requirement that the supersymmetry breaking scale be of order 103−104 GeV and that the mixing between the observed light fermions and the mirror fermions present in N = 2 theories be small («mW), make it difficult to construct finite grand unified theories based on a large class of simple groups with a realistic symmetry breaking pattern.


Predicting The Proton Mass From Pi-Pi-Scattering Data, Jf Donoghue, E Golowich, Br Holstein Dec 1983

Predicting The Proton Mass From Pi-Pi-Scattering Data, Jf Donoghue, E Golowich, Br Holstein

Barry R Holstein

We relate experimental information on ππ scattering to tree-level effective chiral Lagrangians. The result is of a form similar to that used in Skyrme-type models of the proton, where the nucleons are described as topologically stable solitons of the chiral fields. In such models, one can express the proton mass in terms of measured scattering data, with the result Mp=880±300 MeV. We interpret this as a consistency test for the Skyrme models.


Kaon Decays And A Determination Of The Scale Of Chiral Symmetry, John Donoghue, E. Golowich, Barry Holstein Dec 1983

Kaon Decays And A Determination Of The Scale Of Chiral Symmetry, John Donoghue, E. Golowich, Barry Holstein

John Donoghue

Using effective chiral Lagrangians, we consider the occurrence of quadratic terms in the AI =I E—+3m matrix element. The inclusion of higher-derivative Lagrangians leads to a significant improvement over the usual current-algebra analysis. This allows an extraction directly from experimental data of Az, a measure of the scale of chiral symmetry. %'e give an operational definition of the chiral scale, and find A&-1 GeV. The issue of uncertainty in the phenomenological determination of the Sparameter is clarified. 


The Temperature Measured By A Uniformly Accelerated Observer, John Donoghue Dec 1983

The Temperature Measured By A Uniformly Accelerated Observer, John Donoghue

John Donoghue

By use of elementary quantum-mechanical arguments we demonstrate how an observer with uniform acceleration a percieves himself as immersed in a heat bath of temperature kT=axn/2pic.


The Gluon "Mass" In The Bag Model, John Donoghue Dec 1983

The Gluon "Mass" In The Bag Model, John Donoghue

John Donoghue

Bernard has proposed a measure of the effective gluon "mass" in terms of the screening of the linear potential for adjoint sources, and has extracted an estimate of mE ——500—800 MeV from a lattice Monte Carlo calculation. The same quantity is calculated in the bag model, with the result m~ ——740+100 MeV. This arises as an effect of confinement, even though the gluons themselves are massless. The model illustrates several interesting features of this measure of "mass", and these are discussed. 


Renormalization Of The Energy Momentum Tensor And The Validity Of The Equivalence Principle At Finite Temperature, John Donoghue, Barry Holstein, R.W. Robinett Dec 1983

Renormalization Of The Energy Momentum Tensor And The Validity Of The Equivalence Principle At Finite Temperature, John Donoghue, Barry Holstein, R.W. Robinett

John Donoghue

Using the techniques of finite-temperature field theory we renormalize the electromagnetic and gravitational couplings of an electron which is immersed in a heat bath with T≪me. By taking the nonrelativistic limit, we demonstrate that the inertial and gravitational masses are unequal. The implications for the equivalence principle are discussed.


Chiral Symmetry And The Penguin Interaction, John Donoghue Dec 1983

Chiral Symmetry And The Penguin Interaction, John Donoghue

John Donoghue

It is shown how the "penguin" interaction, propo"ed by Shifman, Vainshtein, and Zakharov in the theory of nonleptonic weak decays, is consistent with the constraints of chiral symmetry. For the K-m. transition this involves including a diagram which was missed in previous work. The formulas for the %~2m matrix elements are found to be a factor of 2 larger than the original estimates using the vacuum-saturation method. In addition the equivalence of a procedure using a normalordered operator and the more standard technique is demonstrated. 


Electromagnetic Decays Of Glueballs, John Donoghue Dec 1983

Electromagnetic Decays Of Glueballs, John Donoghue

John Donoghue

The magnetic dipole radiative decay of a J =0 + glueball is considered within the MIT bag model. The resultant width, due to gluonic coupling to quarks, is sizable. In addition to g-gglueball mixing, other contributions are found to be significant. We comment that, for magnetic dipole transitions, the radiative widths of glueballs can be expected to be larger than those of radially excited QQ mesons, due to wave-function-orthogonality effects in the latter case. 


Predicting The Proton Mass From Pipi Scattering Data, John Donoghue, E. Golowich, Barry Holstein Dec 1983

Predicting The Proton Mass From Pipi Scattering Data, John Donoghue, E. Golowich, Barry Holstein

John Donoghue

We relate experimental information on 7r7r scattering to tree-level effective chiral Lagrangians. The result is of a form similar to that used in Skyrme-type models of the proton, where the nucleons are described as topologically stable solitons of the chiral fields. In such models, one can express the proton mass in terms of measured scattering data, with the result M~ = 880 + 300 MeV, We interpret this as a consistency test for the Skyrme models. PACS numbers: 11.30.Rd, 12.25.Ht, 12.70.+q, 14.20.Dh 


Direct Quark Model Calculation Of Weak Nonleptonic Matrix Elements, John Donoghue Dec 1983

Direct Quark Model Calculation Of Weak Nonleptonic Matrix Elements, John Donoghue

John Donoghue

It is shown how wave-packet techniques developed by Donoghue and Johnson may be utilized to calculate parity-violating nonleptonic hyperon decay amplitudes directly —without the use of current algebra and PCAC (partial conservation of axial-vector current}. 


Long Distance Chiral Contribution To The Klks Mass Difference, John Donoghue, Eugene Golowich, Barry R. Holstein Dec 1983

Long Distance Chiral Contribution To The Klks Mass Difference, John Donoghue, Eugene Golowich, Barry R. Holstein

John Donoghue

We use chiral symmetry to calculate the very long distance contributions to the KL - KS mass difference. We determine that the dominant effect arises from the two-pion dispersive contribution, which by itself produces a large result comparable to or greater than the experimental mass difference (with the correct sign). Some contributions from intermediate distance are also estimated and could be significant. These conclusions reinforce the need, first pointed out by Wolfenstein, to include an additive parameter to account for the long distance contributions in phenomenological studies of the KL - KS mass difference. The parameter may be determined from the data ...