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Full-Text Articles in Physics
Convexity Of The Free Energy In Some Real-Space Renormalization-Group Approximations, Miron Kaufman, Robert B. Griffiths
Convexity Of The Free Energy In Some Real-Space Renormalization-Group Approximations, Miron Kaufman, Robert B. Griffiths
Miron Kaufman
Whereas the free energy for a spin system in a hierarchical lattice will be convex as a function of appropriate parameters (and thus the heat capacity positive, etc.), the same need not be true of a corresponding approximate real-space renormalization-group method applied to a Bravais lattice. Some examples are given which illustrate this point.
Competing Criticality Of Short- And Infinite-Range Interactions On The Cayley Tree, Mehran Kardar, Miron Kaufman
Competing Criticality Of Short- And Infinite-Range Interactions On The Cayley Tree, Mehran Kardar, Miron Kaufman
Miron Kaufman
The Ising model, with equivalent-neighbor and nearest-neighbor interactions of Cayley tree connectivity, is solved exactly. Breaking translational symmetry by turning on the Cayley interactions is analogous to lowering spatial dimensionality in Bravais lattices. A range of classical criticality, a point of logarithmic corrections, a range of continuously varying power-law singularities, and a point of exponential singularity are successively encountered.
Renormalization And Radiative-Corrections At Finite Temperature, Jf Donoghue, Br Holstein
Renormalization And Radiative-Corrections At Finite Temperature, Jf Donoghue, Br Holstein
Barry R Holstein
We discuss the renormalization prescription for fermions at finite temperature and describe the procedure for calculating radiative corrections. Novel features arise, such as a lack of explicit Lorentz invariance, 1k2 singularities, and the absorption of soft photons from the background heat bath. The methods are illustrated by explicit calculation of the electron renormalization and the radiative corrections to H-->e+e- (with H being spin zero) in finite-temperature QED.
Equatorial Disturbance Dynamo Electric Fields, Bela G. Fejer, M. F. Larsen, D. T. Farley
Equatorial Disturbance Dynamo Electric Fields, Bela G. Fejer, M. F. Larsen, D. T. Farley
Bela G. Fejer
F-region vertical drift data from Jicamarca, Peru show that equatorial east-west electric fields are sometimes perturbed 16-24 hours after the onset of geomagnetic storms. These disturbance dynamo electric fields, which must be caused primarily by the action of neutral winds at low and middle latitudes, decrease and sometimes even reverse the quiet time electric field pattern during both daytime and nighttime. The long delay excludes the possibility that gravity waves are responsible and suggests that the thermospheric circulation is disturbed. The data also show that after some storms there are no such delayed disturbances, a fact which may be due …
Studies Of Self-Focusing Instability At Arecibo, D. T. Farley, C. Lahoz, Bela G. Fejer
Studies Of Self-Focusing Instability At Arecibo, D. T. Farley, C. Lahoz, Bela G. Fejer
Bela G. Fejer
Precisely simultaneous radar and satellite measurements at the altitude of reflection of a strong HF heating wave above the Arecibo Observatory were made on June 7, 1977. Parametric instabilities produce strong enhancements in the plasma line and ion line incoherent scatter radar echoes. These echoes also exhibit periodic deep fading that is attributed to a self-focusing instability. This explanation was confirmed by the in situ observation of electron density fluctuations with peak-to-peak amplitudes reaching at least 3% and a spatial dependence that corresponded closely to the radar fading pattern, at least for irregularity wavelengths ranging from a few hundred meters …
Dislocations And The Nematic To Smectic-A Transition For Arbitrary Values Of K1, Anthony Day, T. Lubensky, A. Mckane
Dislocations And The Nematic To Smectic-A Transition For Arbitrary Values Of K1, Anthony Day, T. Lubensky, A. Mckane
Anthony Roy Day
The de Gennes model is used to derive the energy of interacting dislocations in smectic-A liquid crystals. This energy reduces to the energy of interacting vortices in type-II superconductors when the splay elastic constant K1 is zero and to that derived from the Landau-Peierls elastic energy when spatial variations are slow on a scale of the bend and twist penetration depths. Furthermore, it has a well-defined K1→∞ limit. The dislocation energy is used to study the nematic—to—smectic-A transition as a function of K1 in two dimensions and in 4-ε dimensions. No evidence for the Nelson-Toner, anisotropic critical point is found …
First Vhf Auroral Radarinterferometer Observations, J. Providakes, W. E. Swartz, D. T. Farley, Bela G. Fejer
First Vhf Auroral Radarinterferometer Observations, J. Providakes, W. E. Swartz, D. T. Farley, Bela G. Fejer
Bela G. Fejer
The radar interferometer technique first used at the magnetic equator in Peru is also a very powerful means for studying auroral plasma instabilities. We present here the first results, obtained with a 49.92 MHz, 20-25 KW peak power pulsed radar located in Ithaca, NY (42.5° N, 76.4° W). Strong auroral echoes were obtained during several highly active periods. Phase differences between the signals received on the two antennas accurately determine the E-W position, within the scattering volume, of localized scattering centers, and changes in this phase determine the corresponding velocity. The signal Doppler shift describes radial (essentially N-S) motion. The …
Bound-States, Virtual States, And Non-Exponential Decay Via Path-Integrals, Br Holstein
Bound-States, Virtual States, And Non-Exponential Decay Via Path-Integrals, Br Holstein
Barry R Holstein
Using path integral techniques we demonstrate how three quantum-mechanical phenomena-alpha decay, nonexponential decay, and resonant scattering-can be treated. This procedure is an algebraic one yet reproduces the usual results obtained via solution of the Schrödinger equation via WKB methods.