Showing papers in "Physical Review Letters in 1978"
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TL;DR: In this article, it was pointed out that a global U(1) symmetry, introduced in order to preserve the parity and time-reversal invariance of strong interactions despite the effects of instantons, would lead to a neutral pseudoscalar boson, the "axion", with mass roughly of order 100 keV to 1 MeV.
Abstract: It is pointed out that a global U(1) symmetry, that has been introduced in order to preserve the parity and time-reversal invariance of strong interactions despite the effects of instantons, would lead to a neutral pseudoscalar boson, the "axion," with mass roughly of order 100 keV to 1 MeV. Experimental implications are discussed.
4,138 citations
TL;DR: In this article, the color gauge theory of strong interactions without arbitrary adjustment of parameters is analyzed and several possibilities are identified, including one which would give a remarkable new kind of very light, long-lived pseudoscalar boson.
Abstract: The requirement that P and T be approximately conserved in the color gauge theory of strong interactions without arbitrary adjustment of parameters is analyzed. Several possibilities are identified, including one which would give a remarkable new kind of very light, long-lived pseudoscalar boson.
3,878 citations
TL;DR: In this article, the authors explain the collapse of polyacrylamide gels in terms of mean field theory based on the extension of Flory's formula for free energy of gels.
Abstract: Collapse of polyacrylamide gels is observed upon changing temperature or fluid composition. It is explained in terms of mean-field theory based on the extension of Flory's formula for free energy of gels. Theory predicts, and I have observed, existence of a critical endpoint in the phase equilibria.
1,383 citations
TL;DR: In this article, the consequences of dislocation-mediated two-dimensional melting are worked out for triangular lattices, and the critical behavior, as well as the effect of a periodic substrate, is discussed.
Abstract: The consequences of a theory of dislocation-mediated two-dimensional melting are worked out for triangular lattices. Dissociation of dislocation pairs first drives a transition into a "liquid crystal" phase with exponential decay of translational order, but power-law decay of sixfold orientational order. A subsequent dissociation of disclination pairs at a higher temperature then produces an isotropic fluid. The critical behavior, as well as the effect of a periodic substrate, is discussed.
1,240 citations
TL;DR: In this paper, the authors derived formulas for the electron thermal conductivity in the collisional and collisionless limits for the case of destroyed magnetic surfaces and showed that these formulas can be used to derive a collision-free model of the electron conductivity.
Abstract: Formulas for the electron thermal conductivity have been derived in the collisional and collisionless limits for the case of destroyed magnetic surfaces.
1,128 citations
TL;DR: In this paper, the quasiparticle recombination time in a strong-coupled superconductor was measured by measuring the lifetime-broadened energy gap edge, and agreement with the calculated value was excellent.
Abstract: We have measured the quasiparticle recombination time in the strong-coupled superconductor ${\mathrm{Pb}}_{0.9}$${\mathrm{Bi}}_{0.1}$ directly by measuring the lifetime-broadened energy gap edge. This is done by measuring the $I\ensuremath{-}V$ characteristics of a superconducting tunnel junction of the type ${\mathrm{Pb}}_{0.9}$${\mathrm{Bi}}_{0.1}$-insulator-${\mathrm{Pb}}_{0.9}$${\mathrm{Bi}}_{0.1}$. Agreement with the calculated value is excellent.
968 citations
TL;DR: In this article, the core-hole Auger decay mechanism for impact-induced desorption has been investigated and shown to correlate with the ionization potential of the highest-lying atomic core levels.
Abstract: We present evidence for a fundamentally new mechanism for impact-induced desorption, viz., core-hole Auger decay. We thereby explain why observed thresholds for electron-stimulated desorption (ESD) of positive ions (${\mathrm{O}}^{+}$, O${\mathrm{H}}^{+}$, and ${\mathrm{F}}^{+}$) from certain $d$-band metal oxides (Ti${\mathrm{O}}_{2}$, ${\mathrm{V}}_{2}$${\mathrm{O}}_{5}$, and W${\mathrm{O}}_{3}$) correlate in energy with the ionization potential of the highest-lying atomic core levels. We conclude that electron-stimulated desorption is in many interesting cases an atom-specific, valence-sensitive probe of surfaces.
886 citations
TL;DR: In this article, a procedure which reconciles long parallel wavelength, characteristic of plasma instabilities, with periodicity in a sheared toroidal magnetic field is described and applied to the problem of high-n$ ballooning modes in tokamaks.
Abstract: A procedure which reconciles long parallel wavelength, characteristic of plasma instabilities, with periodicity in a sheared toroidal magnetic field is described. Applied to the problem of high-$n$ ballooning modes in tokamaks it makes possible a full minimization of the potential energy functional $\ensuremath{\delta}W$ and shows that previous calculations overestimated stability.
693 citations
TL;DR: In this article, the first observation of radiation-pressure cooling on a system of resonant absorbers which are elastically bound to a laboratory fixed apparatus was reported, and they were cooled to 40 K by irradiating them with the 8-ensuremath{\mu}W output of a frequency doubled, single-mode dye laser tuned to the low-frequency side of the Doppler profile on the $S 2S 1/2
Abstract: We report the first observation of radiation-pressure cooling on a system of resonant absorbers which are elastically bound to a laboratory fixed apparatus. Mg ii ions confined in a Penning electromagnetic trap are cooled to 40 K by irradiating them with the 8-\ensuremath{\mu}W output of a frequency doubled, single- mode dye laser tuned to the low- frequency side of the Doppler profile on the $^{2}S_{\frac{1}{2}}\ensuremath{\leftrightarrow}^{2}P_{\frac{3}{2}}$ (${M}_{J}=+\frac{1}{2}\ensuremath{\leftrightarrow}{M}_{J}=+\frac{3}{2}$ or ${M}_{J}=\ensuremath{-}\frac{1}{2}\ensuremath{\leftrightarrow}{M}_{J}=\ensuremath{-}\frac{3}{2}$) transitions. Cooling to approximately ${10}^{\ensuremath{-}3}$ K should be possible.
556 citations
TL;DR: In this article, the toroidal electron currents, which sustain the poloidal magnetic field in tokamaks, may be generated by injecting waves with net parallel momentum into the plasma via phased waveguide arrays.
Abstract: Continuous toroidal electron currents, which sustain the poloidal magnetic field in tokamaks, may be generated by injecting waves with net parallel momentum into the plasma via phased waveguide arrays. Waves with high phase velocity can produce a current capable of confining a reactor plasma so that steady-state tokamak operation with acceptable power dissipation becomes possible.
549 citations
TL;DR: In this article, it was shown that the electrical conductivity of carbon polyvinylchloride composites can be attributed to a novel mechanism of tunneling with potential-barrier modulation by thermal fluctuations.
Abstract: We present evidence that in carbon-polyvinylchloride composites, consisting of aggregates of carbon spheres (100-400 \AA{}) dispersed in the insulating matrix, the electrical conductivity can be ascribed to a novel mechanism of tunneling with potential-barrier modulation by thermal fluctuations. Theoretical consideration of the tunneling-probability modification by thermal fluctuating electric field across tunnel junctions yields expressions for the temperature and the field dependences of the conductivity in excellent accord with experimental results.
TL;DR: In this paper, the authors estimate the cross section for Higgs-boson production in proton-proton collisions, and they find that most of the cross-section comes from a two-gluon annihilation process, in which the gluons couple to Higgs bosons via heavy-quark loops.
Abstract: We estimate the cross section for Higgs-boson production in proton-proton collisions. We find that most of the cross section comes from a two-gluon annihilation process, in which the gluons couple to Higgs bosons via heavy-quark loops.
TL;DR: In this paper, a method of stably trapping, cooling, and manipulating atoms on a continuous-wave basis using resonance radiation pressure forces is proposed using highly focused laser beams and atomic beam injection should give a very deep trap for confining single atoms or gases at temperatures
Abstract: A method of stably trapping, cooling, and manipulating atoms on a continuous-wave basis is proposed using resonance radiation pressure forces. Use of highly focused laser beams and atomic beam injection should give a very deep trap for confining single atoms or gases at temperatures \ensuremath{\sim} ${10}^{\ensuremath{-}6}$ \ifmmode^\circ\else\textdegree\fi{}K. An analysis of the saturation properties of radiation pressure forces is given.
TL;DR: In this article, an assemblage of 50 ions, contained in a parabolic well, has been visually observed and cooled by means of near-resonant laser irradiation, and the results show that the irradiation can be very effective.
Abstract: An assemblage of 50 ${\mathrm{Ba}}^{+}$ ions, contained in a parabolic well, has been visually observed and cooled by means of near-resonant laser irradiation.
TL;DR: In this article, the authors studied the superfluid transition of a thin two-dimensional helium film adsorbed on an oscillating substrate and analyzed its mass and dissipation in terms of dynamic theory.
Abstract: We have studied the superfluid transition of a thin two-dimensional helium film adsorbed on an oscillating substrate. The superfluid mass and dissipation when analyzed in terms of the dynamic theory of Ambegaokar, Halperin, Nelson, and Siggia support the Kosterlitz-Thouless picture of the phase transition in a two-dimensional superfluid. The value for the jump in the superfluid density at the transition given by Kosterlitz and Thouless, ${\ensuremath{\rho}}_{s}({{T}_{c}}^{\ensuremath{-}})=8\ensuremath{\pi}{k}_{\mathrm{B}}{(\frac{m}{h})}^{2}{T}_{c}$, is in good agreement with estimates from experiment.
TL;DR: Very general symmetry considerations uniquely favor a bcc crystal structure near the melting line as discussed by the authors, which agrees with observations that almost all metals on the left-hand side of the periodic table are bcc at high temperature, and that even where other structures are more stable, the first phase nucleated on rapid cooling can be bcc.
Abstract: Very general symmetry considerations uniquely favor a bcc crystal structure near the melting line. This agrees with observations that almost all metals on the left-hand side of the periodic table are bcc at high temperature, and that, even where other structures are more stable, the first phase nucleated on rapid cooling can be bcc. Furthermore, icosahedral local symmetries are favored in amorphous solids. Fluctuation effects cause the transition from isotropic liquid to crystal to be first order in any dimension.
TL;DR: In this paper, the dominance of matter over antimatter in the present universe is a consequence of baryon-number nonconserving reactions in the very early fireball, and a computation in specific SU(5) models gives a small ratio of Baryon to photon-number density in rough agreement with observation.
Abstract: I suggest that the dominance of matter over antimatter in the present universe is a consequence of baryon-number--nonconserving reactions in the very early fireball. Unified gauge theories of weak, electromagnetic, and strong interactions provide a basis for such a conjecture and a computation in specific SU(5) models gives a small ratio of baryon- to photon-number density in rough agreement with observation.
TL;DR: In this article, a set of rotationally invariant observables which characterizes the shapes of events is presented, and is calculable in quantum-chromodynamics perturbation theory for final states consisting of quarks and gluons.
Abstract: We present a set of rotationally invariant observables which characterizes the "shapes" of events, and is calculable in quantum-chromodynamics perturbation theory for final states consisting of quarks and gluons ($G$). We include the effects of fragmentation to hadrons in comparing the shapes of events from the processes ${e}^{+}{e}^{\ensuremath{-}}\ensuremath{\rightarrow}q\overline{q}$, ${e}^{+}{e}^{\ensuremath{-}}\ensuremath{\rightarrow}q\overline{q}G$, and ${e}^{+}{e}^{\ensuremath{-}}\ensuremath{\rightarrow}\mathrm{heavy}\mathrm{resonance}\ensuremath{\rightarrow}\mathrm{GGG}$, and from heavy-quark and lepton production. We indicate how our analysis may be extended to deep-elastic lepton-hadron interactions and hadron-hadron collisions involving large transverse momenta.
TL;DR: The edge of the gap in the distribution of Yang-Lee zeros at $H=i{H}_{0}(T)$ on the imaginary magnetic field axis in ferromagnets above ${T}_{c}$ is essentially a critical point.
Abstract: The edge of the gap in the distribution of Yang-Lee zeros at $H=i{H}_{0}(T)$ on the imaginary magnetic field axis in ferromagnets above ${T}_{c}$ is essentially a critical point. In terms of the edge exponents $\ensuremath{\delta}$ and $\ensuremath{\eta}$, the density of zeros obeys $\mathcal{G}({H}^{\ensuremath{'}\ensuremath{'}})\ensuremath{\sim}{[{H}^{\ensuremath{'}\ensuremath{'}}\ensuremath{-}{H}_{0}(T)]}^{\ensuremath{\sigma}}$, with $\ensuremath{\sigma}=\frac{1}{\ensuremath{\delta}}=\frac{(d\ensuremath{-}2+\ensuremath{\eta})}{({d}_{2}\ensuremath{-}\ensuremath{\eta})}$. Classical behavior ($\ensuremath{\sigma}=\frac{1}{2}$) occurs for $dg{d}^{\ifmmode\times\else\texttimes\fi{}}=6$. The appropriate field-theoretic renormalization group entails a $w{\ensuremath{\phi}}^{3}$ coupling and, with $\ensuremath{\epsilon}=6\ensuremath{-}dg~0$, yields $\ensuremath{\eta}\ensuremath{\approx}\ensuremath{-}\frac{\ensuremath{\epsilon}}{9}$ for all $nl\ensuremath{\infty}$. This correlates well with refined series estimates for $d=2$ and $d=3$ and with exact results for $d=1$ ($\ensuremath{\eta}=\ensuremath{-}1$).
TL;DR: In this paper, a scaling theory is used to show that the properties of the asymmetric Anderson model are universal functions of the scaling invariants, and that the susceptibility of a ground state is a function of the sensitivity of the ground state.
Abstract: A scaling theory is used to show that for temperatures $T\ensuremath{\ll}U$, the properties of the asymmetric Anderson model ($U\ensuremath{\gg}|{E}_{d}|, \ensuremath{\Delta}$) are universal functions of the scaling invariants $\ensuremath{\Delta}$ and ${{E}_{d}}^{*}={E}_{d}+(\frac{\ensuremath{\Delta}}{\ensuremath{\pi}})\mathrm{ln}(\frac{{W}_{0}}{\ensuremath{\Delta}})$, where ${W}_{0}$ is the conduction electron bandwidth or $U$, whichever is smaller. Crossovers between various regimes of simple behavior as the temperature changes are described. $|{{E}_{d}}^{*}|\ensuremath{\lesssim}\ensuremath{\Delta}$ is identified as the criterion for a "mixed-valence" ground state, where the susceptibility $\ensuremath{\approx}{\ensuremath{\Delta}}^{\ensuremath{-}1}$. For $\ensuremath{-}{{E}_{d}}^{*}\ensuremath{\gg}\ensuremath{\Delta}$, there is a local-moment regime with a Kondo temperature ${T}_{\mathrm{K}}\ensuremath{\approx}\ensuremath{\Delta}\mathrm{exp}(\frac{\ensuremath{\pi}{{E}_{d}}^{*}}{2\ensuremath{\Delta}})$.
TL;DR: The nonlinear realization of supersymmetry of Volkov and Akulov is related to a constrained linear realization in two and four dimensions as mentioned in this paper, which is the basis for our work.
Abstract: The nonlinear realization of supersymmetry of Volkov and Akulov is related to a constrained linear realization in two and four dimensions.
TL;DR: In this paper, a model of a deformed nucleus in which protons and neutrons are described as interacting rigid rotors with axial symmetry was studied, and a magnetic-dipole collective state describing rotational oscillations of protons against neutrons was predicted.
Abstract: We study a model of a deformed nucleus in which protons and neutrons are described as interacting rigid rotors with axial symmetry. The nucleus as a whole is no longer axially symmetric. A magnetic-dipole collective state describing rotational oscillations of protons against neutrons is predicted.
TL;DR: In this paper, the surface-atom $4f$ level is shifted 0.40 eV to lower binding energy relative to the bulk value, and the surface density of states is narrowed by (7.6 \ifmmode\pm\else\textpm\fi{} 1.1)%.
Abstract: X-ray photoemission spectra of $4f$ and valence electrons in surface atoms of gold have been obtained. The surface-atom $4f$ level is shifted 0.40\ifmmode\pm\else\textpm\fi{}0.01 eV to lower binding energy relative to the bulk value. The surface density of states is narrowed by (7.6 \ifmmode\pm\else\textpm\fi{} 1.1)% and its center of gravity is shifted to lower binding energy by 0.51\ifmmode\pm\else\textpm\fi{}0.08 eV. A model is proposed to account for the core-level shift in terms of the modified surface density of states.
TL;DR: In this article, it was shown that a class of modified Bessel-function distributions may have special significance in describing the statistics of radiation scattered by media characterized by a wide range of length scales, and that these distributions may be obtained mathematically by applying a limit procedure to the random walk problem with a variable number of steps.
Abstract: Evidence is presented which suggests that a class of modified Bessel-function distributions may have special significance in describing the statistics of radiation scattered by media characterized by a wide range of length scales. It is shown that these distributions may be obtained mathematically by applying a limit procedure to the random-walk problem with a variable number of steps. The choice of distribution for the step-number fluctuations is briefly discussed.
TL;DR: In this paper, a molecular-dynamcis study of silver diffusion in superionic conductor AgI is performed, where the potentials are constructed using Pauling's ideas of ionic radii and the diffusion constant for silver and its temperature dependence are in good agreement with experiment.
Abstract: A molecular-dynamcis study of silver diffusion in superionic conductor $\ensuremath{\alpha}$-AgI is performed. Interionic potentials are constructed using Pauling's ideas of ionic radii. The diffusion constant for silver and its temperature dependence are in good agreement with experiment. Good agreement is also obtained for the silver density map with the experiment of Cava, Reidinger, and Wuensch.
TL;DR: In this paper, the authors demonstrated the feasibility of Doppler-free two-photon spectroscopy with a train of picosecond standing-wave light pulses from a synchronously pumped mode-locked cw dye laser.
Abstract: We have demonstrated the feasibility of Doppler-free two-photon spectroscopy with a train of picosecond standing-wave light pulses from a synchronously pumped mode-locked cw dye laser. The actively controlled mode spectrum provides a means for accurate measurements of large frequency intervals. From a multipulse spectrum of the sodium $3s\ensuremath{-}4d$ transition we have determined a new value of the $4d$ fine-structure splitting, 1028\ifmmode\pm\else\textpm\fi{}0.4 MHz.
PARC1
TL;DR: In this article, the (110) surface atomic geometries of GaAs and ZnSe and of 2 \ifmmode\times\else\texttimes\fi{} 1 reconstructed (111) surface of Si are calculated by minimizing the total energy of the electron-ion system.
Abstract: The (110) surface atomic geometries of GaAs and ZnSe and of 2 \ifmmode\times\else\texttimes\fi{} 1 reconstructed (111) surface of Si are calculated by minimizing the total energy of the electron-ion system. The corresponding reductions in total energy between the relaxed and unrelaxed surfaces are calculated to be - 0.51, - 0.30, and - 0.37 eV per surface atom, respectively. Subsurface relaxations are generally found to make a very small (\ensuremath{\le} 0.02 eV) contribution to the reduction in total energy.
TL;DR: In this article, an experimental measure for a precise test of quantum chromodynamics is presented for the asymmetry in the energy-weighted opening angles of the jets of hadrons produced in the process.
Abstract: An experimental measure is presented for a precise test of quantum chromodynamics. This measure involves the asymmetry in the energy-weighted opening angles of the jets of hadrons produced in the process ${e}^{+}{e}^{\ensuremath{-}}\ensuremath{\rightarrow}\mathrm{hadrons}$ at energy $W$. It is special for several reasons: It is reliably calculable in asymptotically free perturbation theory; it has rapidly vanishing (order $\frac{1}{{W}^{2}}$) corrections due to nonperturbative confinement effects; and it is straightforward to determine experimentally.