Open Access. Powered by Scholars. Published by Universities.®

Physics Commons

Open Access. Powered by Scholars. Published by Universities.®

Articles 1 - 28 of 28

Full-Text Articles in Physics

Community Structure In Introductory Physics Course Networks, Adrienne L. Traxler Jul 2015

Community Structure In Introductory Physics Course Networks, Adrienne L. Traxler

Physics Faculty Publications

Student-to-student interactions are foundational to many active learning environments, but are most often studied using qualitative methods. Quantitative network analysis tools complement this picture, allowing researchers to describe the social interactions of whole classrooms as systems. Past results in introductory physics have suggested a sharp division in the formation of social structure between large lecture sections and small studio classroom environments. Extending those results, this study focuses on calculus-based introductory physics courses at a large public university with a heavily commuter and nontraditional student population. Community detection network methods are used to characterize pre- and post-course collaborative structure in several ...


Confinement-Deconfinement Transition As An Indication Of Spin-Liquid-Type Behavior In Na2Iro3, Zhanybek Alpichshev, Fahad Mahmood, Gang Cao, Nuh Gedik Jan 2015

Confinement-Deconfinement Transition As An Indication Of Spin-Liquid-Type Behavior In Na2Iro3, Zhanybek Alpichshev, Fahad Mahmood, Gang Cao, Nuh Gedik

Physics and Astronomy Faculty Publications

We use ultrafast optical spectroscopy to observe binding of charged single-particle excitations (SE) in the magnetically frustrated Mott insulator Na2IrO3. Above the antiferromagnetic ordering temperature (TN) the system response is due to both Hubbard excitons (HE) and their constituent unpaired SE. The SE response becomes strongly suppressed immediately below TN. We argue that this increase in binding energy is due to a unique interplay between the frustrated Kitaev and the weak Heisenberg-type ordering term in the Hamiltonian, mediating an effective interaction between the spin-singlet SE. This interaction grows with distance causing the SE to become ...


Direct Observation Of Quark-Hadron Duality In The Free Neutron F2 Structure Function, I. Niculescu, G. Niculescu, W. Melnitchouk, J. Arrington, M. E. Christy, S. Kuhn Jan 2015

Direct Observation Of Quark-Hadron Duality In The Free Neutron F2 Structure Function, I. Niculescu, G. Niculescu, W. Melnitchouk, J. Arrington, M. E. Christy, S. Kuhn

Physics Faculty Publications

Using the recently published data from the BONuS(Barely Off-shell Nucleon Structure) experiment at Jefferson Lab, which utilized a spectator tagging technique to extract the inclusive electron-free neutron scattering cross section, we obtain the first direct observation of quark-hadron duality in the neutron F2 structure function. The data are used to reconstruct the lowest few (N = 2, 4, and 6) moments of F2 in the three prominent nucleon resonance regions, as well as the moments integrated over the entire resonance region. Comparison with moments computed from global parametrizations of parton distribution functions suggest that quark-hadron duality holds locally ...


Advances In The Analysis And Prediction Of Turbulent Viscoelastic Flows, T. B. Gatski, L. Thais, G. Mompean Jan 2014

Advances In The Analysis And Prediction Of Turbulent Viscoelastic Flows, T. B. Gatski, L. Thais, G. Mompean

CCPO Publications

It has been well-known for over six decades that the addition of minute amounts of long polymer chains to organic solvents, or water, can lead to significant turbulent drag reduction. This discovery has had many practical applications such as in pipeline fluid transport, oil well operations, vehicle design and submersible vehicle projectiles, and more recently arteriosclerosis treatment. However, it has only been the last twenty-five years that the full utilization of direct numerical simulation of such turbulent viscoelastic flows has been achieved. The unique characteristics of viscoelastic fluid flow are dictated by the nonlinear differential relationship between the flow strain ...


Microcalorimetric Study Of Nematic-To-Neat-Soap And Nematic-To-Isotropic Phase Transitions In A Lyotropic Liquid Crystal, T. S. Shin, Satyendra Kumar Oct 2013

Microcalorimetric Study Of Nematic-To-Neat-Soap And Nematic-To-Isotropic Phase Transitions In A Lyotropic Liquid Crystal, T. S. Shin, Satyendra Kumar

Satyendra Kumar

The results of specific-heat measurements at the nematic- (N) to-neat-soap (NS) and nematic-to-isotropic (I) phase transitions in binary mixtures of cesium-perfluoro-octanoate and water are reported. The ratio of specific-heat amplitudes above and below the N-NS transition, A+/A-, and the specific-heat exponent α remain ∼1.0 and ≤0.02, respectively, suggesting 3D XY-type behavior. At the first-order N-I transition, vanishing latent heat and coexistence range at low concentration indicate the existence of a Landau point.


A Cellulose Liquid Crystal Motor: A Steam Engine Of The Second Kind, Yong Geng, Pedro Lucio Almeida, Cheng Cheng, Peter Palffy-Muhoray, Maria Helena Godinho, Susete Nogueira Fernandes Oct 2013

A Cellulose Liquid Crystal Motor: A Steam Engine Of The Second Kind, Yong Geng, Pedro Lucio Almeida, Cheng Cheng, Peter Palffy-Muhoray, Maria Helena Godinho, Susete Nogueira Fernandes

Peter Palffy-Muhoray

The salient feature of liquid crystal elastomers and networks is strong coupling between orientational order and mechanical strain. Orientational order can be changed by a wide variety of stimuli, including the presence of moisture. Changes in the orientation of constituents give rise to stresses and strains, which result in changes in sample shape. We have utilized this effect to build soft cellulose-based motor driven by humidity. The motor consists of a circular loop of cellulose film, which passes over two wheels. When humid air is present near one of the wheels on one side of the film, with drier air ...


Pattern Formation In Non-Newtonian Hele-Shaw Flow, P. Fast, L. Kondic, M. J. Shelley, Peter Palffy-Muhoray Oct 2013

Pattern Formation In Non-Newtonian Hele-Shaw Flow, P. Fast, L. Kondic, M. J. Shelley, Peter Palffy-Muhoray

Peter Palffy-Muhoray

We study theoretically the Saffman-Taylor instability of an air bubble expanding into a non-Newtonian fluid in a Hele-Shaw cell, with the motivation of understanding suppression of tip-splitting and the formation of dendritic structures observed in the flow of complex fluids, such as polymeric liquids or liquid crystals. A standard visco-elastic flow model is simplified in the case of flow in a thin gap, and it is found that there is a distinguished limit where shear thinning and normal stress differences are apparent, but elastic response is negligible. This observation allows formulation of a generalized Darcy's law, where the pressure ...


Distance Of Closest Approach Of Two Arbitrary Hard Ellipses In Two Dimensions, Xiaoyu Zheng, Peter Palffy-Muhoray Oct 2013

Distance Of Closest Approach Of Two Arbitrary Hard Ellipses In Two Dimensions, Xiaoyu Zheng, Peter Palffy-Muhoray

Peter Palffy-Muhoray

The distance of closest approach of hard particles is a key parameter of their interaction and plays an important role in the resulting phase behavior. For nonspherical particles, the distance of closest approach depends on orientation, and its calculation is surprisingly difficult. Although overlap criteria have been developed for use in computer simulations [ Vieillard-Baron J. Chem. Phys. 56 4729 (1972); Perram and Wertheim J. Comput. Phys. 58 409 (1985)], no analytic solutions have been obtained for the distance of closest approach of ellipsoids in three dimensions, or, until now, for ellipses in two dimensions. We have derived an analytic expression ...


Effect Of Director Distortions On Morphologies Of Phase Separation In Liquid Crystals, D. Voloschenko, Oleg P. Pishnyak, Sergij V. Shiyanovskii, Oleg Lavrentovich Oct 2013

Effect Of Director Distortions On Morphologies Of Phase Separation In Liquid Crystals, D. Voloschenko, Oleg P. Pishnyak, Sergij V. Shiyanovskii, Oleg Lavrentovich

Oleg Lavrentovich

We study phase separation from a nematic liquid crystal with spatially nonuniform director gradients. Particles of a phase-separated component, which is either an isotropic fluid (silicone oil) or a nonmesogenic photopolymer, accumulate in the regions with the strongest director distortions, thus reducing the overall energy of the system.


Nanophase Segregation Of Nonpolar Solvents In Smectic Liquid Crystals Of Bent-Shape Molecules, M.Y.M. Huang, A.M. Pedreira, O.G. Martins, A.M.F. Neto, Antal Jakli Oct 2013

Nanophase Segregation Of Nonpolar Solvents In Smectic Liquid Crystals Of Bent-Shape Molecules, M.Y.M. Huang, A.M. Pedreira, O.G. Martins, A.M.F. Neto, Antal Jakli

Antal Jakli

Electro-optical, calorimetric, x-ray, and dielectric measurements are reported on a mixture containing a bent-core liquid crystal 4-chloro-1,3-phenylinebis [4-(4-n-tetradecyloxyphenyliminomethyl) benzoate] mixed with the nonpolar solvent n-hexadecane (HEX). It is observed that the addition of HEX depresses the isotropic-to-smectic phase transition temperature, but the crystallization temperature does not change considerably. Instead, the texture of the crystalline phase changes and, at sufficiently high concentrations of HEX (>20 wt %), an optically isotropic phase appears. Above 40 wt % HEX concentrations, the mesophase completely disappears and a direct isotropic solid-to-isotropic liquid transition takes place. At increasing HEX concentration, the transition enthalpies, the layer ordering ...


Light-Induced Changes Of Optical And Electrical Properties In Bent-Core Azo Compounds, Antal Jakli, V. Prasad, D.S.S. Rao, Guangxun Liao, I. Janossy Oct 2013

Light-Induced Changes Of Optical And Electrical Properties In Bent-Core Azo Compounds, Antal Jakli, V. Prasad, D.S.S. Rao, Guangxun Liao, I. Janossy

Antal Jakli

We have studied the optical and electrical properties of two bent-core substances with an azo linkage in their cores. Pump-probe laser studies, direct textural observations, and spectrophotometric recordings show an initial decrease of light transmission, which at larger light intensities (similar to 1 mW/mm(2)) is followed by a bleaching. Simultaneously the electrical properties (electric conductivity, antiferroelectric polarization, switching threshold, and switching time) decreased monotonically with increasing light intensities. The monotonic decrease of electrical properties indicates that the darkening and bleaching have the same origin, namely, the photochemical isomerization of the azo linkage from the trans to the cis ...


Synthesis Of Al2tio5 And Its Effect On The Properties Of Chitosan-Nh4scn Polymer Electrolytes, Siti Rohana Majid, Hassan F., Woo H. J., Aziz N. A., Kufian M. Z. Dec 2012

Synthesis Of Al2tio5 And Its Effect On The Properties Of Chitosan-Nh4scn Polymer Electrolytes, Siti Rohana Majid, Hassan F., Woo H. J., Aziz N. A., Kufian M. Z.

Siti Rohana Majid

In this paper, Al2TiO5 ceramic material has been synthesised and used as filler in polymer electrolyte system to enhance the conductivity. The precursor sintered at 1,050 A degrees C and contained 0.08 mole of aluminium nitrate gives the best and complete formation of Al2TiO5. Composite polymer electrolytes of chitosan-NH4SCN containing different amount of home-made Al2TiO5 were prepared by solution casting. The addition of filler has enhanced the conductivity of polymer electrolyte. The sample 57 wt% chitosan-38 wt% NH4SCN-5 wt% Al2TiO5 exhibited the highest electrical conductivity of 2.10 x 10(-4) S cm(-1) at room temperature. The ...


The Behavior Of A Falling Particle In A Funnel, Tahani Hassn Aldahri Oct 2012

The Behavior Of A Falling Particle In A Funnel, Tahani Hassn Aldahri

Electronic Thesis and Dissertation Repository

Recent theoretical work has suggested that a frictional, inelastic, spherical particle falling under gravity through a symmetric funnel will display interesting behavior as a function of the angle of the funnel walls. We have studied this system experimentally, using high-speed video to record the particle trajectories. By analyzing the video images, we have analyzed the time the ball spends in the funnel and its energy loss as functions of the angle of the walls with respect to the horizontal. The coefficient of restitution was also varied by using different balls and funnel materials. We found some similarities and differences between ...


Scaling Behavior Of The Exchange-Bias Training Effect, Christian Binek, Srinivas Polisetty, Sarbeswar Sahoo Mar 2012

Scaling Behavior Of The Exchange-Bias Training Effect, Christian Binek, Srinivas Polisetty, Sarbeswar Sahoo

Christian Binek

The dependence of the exchange-bias training effect on temperature and ferromagnetic film thickness is studied in detail and scaling behavior of the data is presented. Thickness-dependent exchange bias and its training are measured using the magneto-optical Kerr effect. A focused laser beam is scanned across a Co wedge probing local hysteresis loops of the Co film which is pinned by an antiferromagnetic CoO layer of uniform thickness. A phenomenological theory is best fitted to the exchange-bias training data resembling the evolution of the exchange-bias field on subsequently cycled hysteresis loops. Best fits are done for various temperatures and Co thicknesses ...


Random-Field Critical And Spin-Flop Behavior Of The Anisotropic Heisenberg Antiferromagnet Fe0.9mg0.1br2 In Axial Magnetic Fields, Christian Binek Mar 2012

Random-Field Critical And Spin-Flop Behavior Of The Anisotropic Heisenberg Antiferromagnet Fe0.9mg0.1br2 In Axial Magnetic Fields, Christian Binek

Christian Binek

Faraday optical measurements on the dilute hexagonal antiferromagnet Fe0.85Mg0.15Br2 in an external axial field reveal a spin-flop phase line ending at a multicritical point (Tm=8.1 K, Hm=1050 kA m-1) and crossover from random-exchange to random-field Ising criticality with an exponent Phi =1.40+or-0.04 in the vicinity of TN=11.1 K. Cusp-like behaviour of the specific heat at TN is discussed in view of recent Monte Carlo results.


Preparation And Characterization Of Magnesium Ion Gel Polymer Electrolytes For Application In Electrical Double Layer Capacitors, Siti Rohana Majid, Asmara S. N., Kufian M. Z., Arof A. K. Dec 2010

Preparation And Characterization Of Magnesium Ion Gel Polymer Electrolytes For Application In Electrical Double Layer Capacitors, Siti Rohana Majid, Asmara S. N., Kufian M. Z., Arof A. K.

Siti Rohana Majid

This work describes the preparation and characterization of poly (methyl methacrylate) (PMMA) based gel polymer electrolytes with magnesium triflate (Mg(CF(3)SO(3))(2)) as the ion providing salt. Liquid electrolytes containing 0.4 M Mg(CF(3)SO(3))(2) in solvents comprising different ratios of ethylene carbonate (EC) and diethyl carbonate (DEC) have been prepared at room temperature. The highest conducting electrolyte contains EC and DEC in the weight ratio of 2:1. To the highest conducting liquid electrolyte, 25-50 wt.% PMMA has been added and the mixtures were heated at 80 degrees C for 2 min ...


Self-Assembly, Condensation, And Order In Aqueous Lyotropic Chromonic Liquid Crystals Crowded With Additives, Luana Tortora, Heung-Shik Park, Shin-Woong Kang, Victoria Savaryn, Seung-Ho Hong, Konstantine Kaznatcheev, Daniele Finotello, Samuel Sprunt, Satyendra Kumar, Oleg Lavrentovich Dec 2009

Self-Assembly, Condensation, And Order In Aqueous Lyotropic Chromonic Liquid Crystals Crowded With Additives, Luana Tortora, Heung-Shik Park, Shin-Woong Kang, Victoria Savaryn, Seung-Ho Hong, Konstantine Kaznatcheev, Daniele Finotello, Samuel Sprunt, Satyendra Kumar, Oleg Lavrentovich

Oleg Lavrentovich

Dense multicomponent systems with macromolecules and small solutes attract a broad research interest as they mimic the molecularly crowded cellular interiors. The additives can condense and align the macromolecules, but they do not change the degree of covalentpolymerization. We chose a lyotropic chromonic liquid crystal with reversibly and non-covalently assembled aggregates as a much softer system, reminiscent of “living polymers”, to demonstrate that small neutral and charged additives cause condensation of aggregates with ensuing orientational and positional ordering and nontrivial morphologies of phase separation, such as tactoids and toroids of the nematic and hexagonal columnar phase coexisting with the isotropic ...


Bent-Core Liquid Crystal Elastomers, Rafael Verduzco, Paul Luchette, Seung Ho Hong, John Harden, Elaine Dimasi, Peter Palffy-Muhoray, S. Michael Kilbey Ii, Jim T. Gleeson, Antal Jákli Dec 2009

Bent-Core Liquid Crystal Elastomers, Rafael Verduzco, Paul Luchette, Seung Ho Hong, John Harden, Elaine Dimasi, Peter Palffy-Muhoray, S. Michael Kilbey Ii, Jim T. Gleeson, Antal Jákli

Peter Palffy-Muhoray

Liquid crystal (LC) elastomers with bent-core side-groups incorporate the properties of bent-core liquid crystals in a flexible and self-supporting polymer network. Bent-core liquid crystal elastomers (BCEs) with uniform alignment were prepared by attaching a reactive bent-core LC to poly(hydrogenmethylsiloxane) and crosslinking with a divinyl crosslinker. Phase behavior studies indicate a nematic phase over a wide temperature range that approaches room temperature, and thermoelastic measurements show that these BCEs can reversibly change their length by more than a factor of two upon heating and cooling. Small-angle X-ray scattering studies reveal multiple, broad low-angle peaks consistent with short-range smectic C order ...


Self-Assembly, Condensation, And Order In Aqueous Lyotropic Chromonic Liquid Crystals Crowded With Additives, Luana Tortora, Heung-Shik Park, Shin-Woong Kang, Victoria Savaryn, Seung-Ho Hong, Konstantine Kaznatcheev, Daniele Finotello, Samuel Sprunt, Satyendra Kumar, Oleg Lavrentovich Dec 2009

Self-Assembly, Condensation, And Order In Aqueous Lyotropic Chromonic Liquid Crystals Crowded With Additives, Luana Tortora, Heung-Shik Park, Shin-Woong Kang, Victoria Savaryn, Seung-Ho Hong, Konstantine Kaznatcheev, Daniele Finotello, Samuel Sprunt, Satyendra Kumar, Oleg Lavrentovich

Satyendra Kumar

Dense multicomponent systems with macromolecules and small solutes attract a broad research interest as they mimic the molecularly crowded cellular interiors. The additives can condense and align the macromolecules, but they do not change the degree of covalentpolymerization. We chose a lyotropic chromonic liquid crystal with reversibly and non-covalently assembled aggregates as a much softer system, reminiscent of “living polymers”, to demonstrate that small neutral and charged additives cause condensation of aggregates with ensuing orientational and positional ordering and nontrivial morphologies of phase separation, such as tactoids and toroids of the nematic and hexagonal columnar phase coexisting with the isotropic ...


Light-Driven Molecular Switches With Tetrahedral And Axial Chirality, Lisa Green, Yannian Li, Timothy White, Augustine Urbas, Timothy Bunning, Quan Li Aug 2009

Light-Driven Molecular Switches With Tetrahedral And Axial Chirality, Lisa Green, Yannian Li, Timothy White, Augustine Urbas, Timothy Bunning, Quan Li

Quan Li

Two light-driven molecular switches with tetrahedral and axial chirality were synthesized, which can induce a helical superstructure in an achiral liquid crystal host and dynamically phototune it to achieve reversible reflection color.


Scaling Behavior Of The Exchange-Bias Training Effect, Christian Binek, Srinivas Polisetty, Sarbeswar Sahoo Aug 2007

Scaling Behavior Of The Exchange-Bias Training Effect, Christian Binek, Srinivas Polisetty, Sarbeswar Sahoo

Christian Binek Publications

The dependence of the exchange-bias training effect on temperature and ferromagnetic film thickness is studied in detail and scaling behavior of the data is presented. Thickness-dependent exchange bias and its training are measured using the magneto-optical Kerr effect. A focused laser beam is scanned across a Co wedge probing local hysteresis loops of the Co film which is pinned by an antiferromagnetic CoO layer of uniform thickness. A phenomenological theory is best fitted to the exchange-bias training data resembling the evolution of the exchange-bias field on subsequently cycled hysteresis loops. Best fits are done for various temperatures and Co thicknesses ...


Odd-Even Effects In Bent-Core Compounds Containing Terminal N-Alkyl Carboxylate Groups, S. Umadevi, Antal Jakli, B. Sadashiva Oct 2006

Odd-Even Effects In Bent-Core Compounds Containing Terminal N-Alkyl Carboxylate Groups, S. Umadevi, Antal Jakli, B. Sadashiva

Antal Jakli

A homologous series of eleven five-ring symmetrical bent-core compounds containing terminal n-alkyl carboxylate groups were synthesized, characterized and their dielectric and electro-optical properties have been investigated. The lower homologues (n = 6-11) of the series show B-2 structures with an interesting odd-even effect concerning their local director tilt and polar arrangements. This odd-even effect probably is due to steric (entropic) reasons, which are not suppressed by the relatively low polar interaction. Three of the middle homologues display a B-7' phase, which is bistable and shows linear electro-optical switching with a transition to the chiral antiferroelectric smectic phase at a lower temperature ...


Behavior Of The Ionosphere And Thermosphere Subject To Extreme Solar Cycle Conditions, C. G. Smithtro, Jan Josef Sojka Jan 2005

Behavior Of The Ionosphere And Thermosphere Subject To Extreme Solar Cycle Conditions, C. G. Smithtro, Jan Josef Sojka

All Physics Faculty Publications

A 1-D global average ionosphere and thermosphere (GAIT) model is used to examine the climatological behavior of the upper atmosphere, subject to both extremely low and high solar flux. These extremes are justified, in part, by the Maunder Minimum and Grand Maximum epochs described by J. A. Eddy, as well as other studies involving cosmogenic isotopes and Sun-like stars. As the irradiance falls below normal solar minimum levels, the concentration of O+ decreases rapidly relative to the molecular ions, such that the ratio ƒoF2oF1 approaches unity. When subject to exceptionally high solar fluxes ...


Novel Examples Of Achiral Bent-Core Azo Compounds Exhibiting B1 And Anticlinic-Antiferroelectric B2 Mesophases, Veena Prasad, Shin-Woong Kang, Satyendra Kumar Dec 2002

Novel Examples Of Achiral Bent-Core Azo Compounds Exhibiting B1 And Anticlinic-Antiferroelectric B2 Mesophases, Veena Prasad, Shin-Woong Kang, Satyendra Kumar

Satyendra Kumar

The first examples of achiral bent-core molecules consisting of an azo linkage and five aromatic rings exhibiting bent-core mesophases are reported. They exhibit B1 and B2 phases as identified by optical microscopy, differential scanning calorimetry, X-ray diffraction, and electro-optical techniques. The B2 phase of these materials is identified to be the anticlinic–antiferroelectric, SmCAPA phase. The mesophases of these compounds have relatively low transition temperatures and wide temperature ranges. The observation of bent-core phases in azo compounds assumes significance from the fact that the introduction of the –NN– linkage adds a new dimension, namely photochromism, to this field.


Calorimetric Study Of Nematic Prewetting, Xuewu Liu, David W. Allender, D. Finotello Sep 2002

Calorimetric Study Of Nematic Prewetting, Xuewu Liu, David W. Allender, D. Finotello

David W Allender

We report specific-heat measurements for a series of liquid crystals imbedded in a porous cylindrical geometry. Above the nematic-to-isotropic transition and dependent on nematic width (or chain length), the specific heat shows a small peak. In analogy to known ellipsometry results, the peak is believed to be the signature of a nematic prewetting transition.


Relaxation Dynamics Of Rubbed Polystyrene Thin Films, D. M. G. Agra, A. D. Schwab, J-H. Kim, Satyendra Kumar, A. Dhinojwala Aug 2000

Relaxation Dynamics Of Rubbed Polystyrene Thin Films, D. M. G. Agra, A. D. Schwab, J-H. Kim, Satyendra Kumar, A. Dhinojwala

Satyendra Kumar

Optical retardation measurements were used to probe the chain relaxation dynamics in rubbed polystyrene films of varying thicknesses on glass substrates. A model based on Kohlrausch-Williams-Watts relaxation was developed and used to determine the glass transition temperature (Tg) of the films. Results showed reductions of 15–20 K in Tg for thin films of thicknesses comparable to the radius of gyration as well as for cast films rubbed with different strengths. These results provide evidence of a faster relaxation dynamics relative to the polymer-substrate interface for thinner films and enhanced chain mobility at the polymer-air interface.


Random-Field Critical And Spin-Flop Behavior Of The Anisotropic Heisenberg Antiferromagnet Fe0.9mg0.1br2 In Axial Magnetic Fields, Christian Binek Feb 1994

Random-Field Critical And Spin-Flop Behavior Of The Anisotropic Heisenberg Antiferromagnet Fe0.9mg0.1br2 In Axial Magnetic Fields, Christian Binek

Christian Binek Publications

Faraday optical measurements on the dilute hexagonal antiferromagnet Fe0.85Mg0.15Br2 in an external axial field reveal a spin-flop phase line ending at a multicritical point (Tm=8.1 K, Hm=1050 kA m-1) and crossover from random-exchange to random-field Ising criticality with an exponent Phi =1.40+or-0.04 in the vicinity of TN=11.1 K. Cusp-like behaviour of the specific heat at TN is discussed in view of recent Monte Carlo results.


Symmetry Behavior Of The Static Taub Universe: Effect Of Curvature Anisotropy, T. C. Shen, B. L. Hu, D. J. O'Connor Jan 1985

Symmetry Behavior Of The Static Taub Universe: Effect Of Curvature Anisotropy, T. C. Shen, B. L. Hu, D. J. O'Connor

T. -C. Shen

Using the static Taub universe as an example, we study the effect of curvature anisotropy on symmetry breaking of self-interacting scalar field. The one-loop effective potential of a λφ4 field with arbitrary coupling (ξ) is computed by ζ-function regularization. It is expressed as a perturbative series in a small anisotropy parameter α measuring the deformation from the spherical Einstein universe with radius of curvature α. This result is used for analyzing the symmetry behavior of such a system as a function of the geometric (α,α) and field (ξ,λ) parameters. The result is also used to address the ...