We point out that in systems exhibiting a second-order transition, the chemical potential has a jump in slope at the critical temperature, provided provided that ${\mathit{T}}_{\mathit{c}}$ depends on particle density. We derive a generally valid thermodynamic relation between the specific heat jump, the jump in dμ/dT and dln${\mathit{T}}_{\mathit{c}}$/dn, with μ the chemical potential and n the density of the particles causing the transition. This relation is similar, but not equivalent, to the more familiar Ehrenfest relation between expansivity, specific heat, and dln${\mathit{T}}_{\mathit{c}}$/dp, with p the externally applied pressure.

We report the experimental observation of a discontinuous change in slope at ${\mathit{T}}_{\mathit{c}}$ of the temperature dependence of the work function of ${\mathrm{YBa}}_2$${\mathrm{Cu}}_3$${\mathrm{O}}_{7\mathrm{-}\mathrm{\delta }}$. We interpret this effect as a superconductivity-induced temperature dependence of the chemical potential. Using a general thermodynamic relation for second-order phase transitions and published values of the specific heat jump, we extract a value for d ln${\mathit{T}}_{\mathit{c}}$/dn, with n the charge carrier density. This value is consistent with hole-type superconductivity.

A Monte Carlo simulation of the vortices in a two-dimensional type-II superconductor shows that the correlation length, which measures the range over which triangular lattice ordering of the vortices exists, diverges to infinity in the zero-temperature limit, just as predicted by a scaling argument based on phase fluctuations. No evidence is found for the formation of a vortex lattice phase at a finite temperature.

The generalization of non-Néel spin ordering concept to itinerant systems is discussed. It is shown that some of the p-type spin nematic and chiral spin states affect the electronic spectrum near the Fermi surface and can then be related by symmetry with the intrinsic instabilities of the Fermi liquid although the energetic mechanisms for the localized spins and itinerant electrons are different. If the localized and itinerant subsystems coexist, the phase transition is described by the common order parameter. Possible experimental manifestations of the above transitions are discussed.

We show how the broken symmetries of the Néel state are embodied in the exact spectrum of the triangular Heisenberg antiferromagnet on finite lattices as small as N=21 (spectra up to N=36 have been computer). We present the first numerical evidence of an extensive set of low-lying levels that are below the softest magnons and collapse to the ground state in the thermodynamic limit. This set of quantum states represents the quantum counterpart of the classical Néel ground state. We develop an approach relying on the symmetry analysis and finite-size scaling and we provide new arguments in favor of an ordered ground state for the S=1/2 triangular Heisenberg model.

The two-channel Kondo Hamiltonian has recently been proposed as a description of several experimental systems. Our numerical renormalization-group treatment of a pair of magnetic impurities shows that at low temperatures, interimpurity interactions destabilize the ‘‘marginal-Fermi-liquid’’ behavior predicted by a single-impurity model. We find four stable zero-temperature regimes, three of which can be described by Fermi-liquid theory. The fourth possesses a complex many-body ground state and non-Fermi-liquid properties which are expected to be governed by nonuniversal critical exponents.

We present carbon K emission spectra of diamond excited with high-resolution undulator radiation. The valence-band emission spectra are shown to be strongly dependent on the excitation energy, up to 20–30 eV above the C K edge. It is proposed that the dependence is indicative of the resonant inelastic scattering description of these emission spectra, i.e., the absorption-emission process should be described as a single scattering event where the momenta of the photoelectron and the valence hole in the final state are related by momentum conservation.

We present a computational framework not based on the string hypothesis for the thermodynamics of statistical and quantum field theory models solvable by the Bethe ansatz. In the cases of XXZ Heisenberg chain and the sine-Gordon quantum field theory we derive a single nonlinear integral equation which determines the free energy (or ground-state scaling function). Our approach is very effective at high temperature, and correctly reproduces the low-temperature central charge and the analytic structure of the corrections.

We consider the problem of thermally activated potential barrier crossing in the presence of fluctuations of the barrier itself. For piecewise linear barrier switching between two values as a Markov process, exact and Monte Carlo results reveal a novel resonantlike phenomenon as a function of the barrier fluctuation rate. For very slow variations the average crossing time is the average of the times required to diffuse over each of the barriers separately; for very fast variations the mean crossing time is that required to cross the average barrier. At intermediate rates the crossing is strongly correlated with the potential variation and the escape rate exhibits a local maximum at a ‘‘resonant’’ fluctuation rate.

We introduce and analyze a class of nonlinear Langevin equations that describe electrical transport in systems with electric-field thresholds, such as charge-density-wave systems biased just above threshold. For sufficiently large nonlinearities, the models are argued to exhibit scale-invaraint phases wherein spatial and temporal correlations decay algebraically; in particular, current and voltage fluctuations show 1/${\mathit{f}}^{\mathrm{\alpha }}$ noise with universal exponents α. The values of physical parameters required for the experimental observation of these phases are estimated.

We have measured the Rydberg constant by frequency comparison of the three transitions 2${\mathit{S}}_{1/2\mathrm{-}}$8${\mathit{S}}_{1/2}$, 2${\mathit{S}}_{1/2\mathrm{-}}$8${\mathit{D}}_{3/2}$, and 2${\mathit{S}}_{1/2\mathrm{-}}$8${\mathit{D}}_{5/2}$ in hydrogen with the difference of two optical standards, the methane-stabilized He-Ne laser and the iodine-stabilized He-Ne laser. The frequency of the iodine-stabilized He-Ne laser has been remeasured. The new value for the Rydberg constant, ${\mathit{R}}_{\mathrm{\infty }}$=109 737.315 683 0(31) ${\mathrm{cm}}^{\mathrm{-}1}$, is currently the most precise available.

The understanding of our Universe is based on the working hypothesis that the homogeneous and isotropic models give a successful description on a very large scale, despite the nonlinear inhomogeneity of the matter distribution in the present Universe. We consider the compatibility problem between the overall homogeneity and isotropy and the local inhomogeneity. A scheme to construct inhomogeneous irrotational dust universes which are homogeneous and isotropic on average is shown in the framework of general relativity; they represent ‘‘relativistic pancake solutions’’ analogous to those in Newtonian cosmology.

We have searched for a flux of axions produced in the Sun by exploiting their conversion to x rays in a static magnetic field. The signature of a solar axion flux would be an increase in the rate of x rays detected in a magnetic telescope when the Sun passes within its acceptance. From the absence of such a signal we set a 3σ limit on the axion coupling to two photons ${\mathit{g}}_{\mathit{a}\gamma \gamma }$≡1/M<3.6×${10}^{\mathrm{-}9}$ ${\mathrm{GeV}}^{\mathrm{-}1}$, provided the axion mass ${\mathit{m}}_{\mathit{a}}$<0.03 eV and <7.7×${10}^{\mathrm{-}9}$ ${\mathrm{GeV}}^{\mathrm{-}1}$ for 0.03 <${\mathit{m}}_{\mathit{a}}$<0.11 eV.

We have performed a search for the ${}_{}{}^1{}_{}{}^{}$${\mathit{P}}_1$ state of charmonium resonantly formed in p¯p annihilations, close to the center of gravity of the ${}_{}{}^3{}_{}{}^{}$${\mathit{P}}_{\mathit{J}}$ states. We report results from the study of the J/ψ+${\mathrm{\pi }}^0$ and J/ψ+2π final states. We have observed a statistically significant enhancement in the p¯+p→J/ψ+${\mathrm{\pi }}^0$ cross section at √s ≃3526.2 MeV. This enhancement has the characteristics of a narrow resonance of mass, total width, and production cross section consistent with what is expected for the ${}_{}{}^1{}_{}{}^{}$${\mathit{P}}_1$ state. In our search we have found no candidates for the reactions p¯+p→J/ψ+${\mathrm{\pi }}^0$+${\mathrm{\pi }}^0$ and p¯+p→J/ψ+${\mathrm{\pi }}^{+}$+${\mathrm{\pi }}^{\mathrm{-}}$.

Double beta decay of ${}_{}{}^{128}{}_{}{}^{}\mathrm{Te}$ has been confirmed and the ratio of half-lives for ββ decay of ${}_{}{}^{130}{}_{}{}^{}\mathrm{Te}$ and ${}_{}{}^{128}{}_{}{}^{}\mathrm{Te}$ has been determiend as ${}_{}{}^{130}{}_{}{}^{}\mathrm{Te}_{1/2}^{}{}_{}{}^{}$${/}^{128}$${\mathrm{Te}}_{1/2}$=(3.52±0.11)×${10}^{\mathrm{-}4}$ by ion-counting mass spectrometry of Xe in ancient Te ores. The Xe measurements, combined with common Pb dating, yield a ${}_{}{}^{130}{}_{}{}^{}\mathrm{Te}$ half-life of (2.7±0.1)×${10}^{21}$ yr and thus a ${}_{}{}^{128}{}_{}{}^{}\mathrm{Te}$ half-life of (7.7±0.4)×${10}^{24}$ yr. These results give limits on the effective Majorana mass of the neutrino (<1.1-1.5 eV) and right-handed currents (‖〈η〉‖>5.3×${10}^{\mathrm{-}8)}$ comparable to the best obtained from direct neutrinoless ββ-decay searches. They also imply new limits on nonstandard Majorons not constrained by measurements of the ${\mathit{Z}}^0$ decay width.

We report measurements of d¯, p¯, ${\mathit{K}}^{\mathrm{-}}$, and ${\mathrm{\pi }}^{\mathrm{-}}$ produced at 0° in collisions of 14.6A GeV/c ${}_{}{}^{28}{}_{}{}^{}\mathrm{Si}$ on Al, Cu, and Au targets. A beam-line focusing spectrometer was used to identify particles at rigidities from -2 to -8 GV. The ratio of d¯/p¯ invariant cross sections at midrapidity (y=1.7) is (1±0.7)×${10}^{\mathrm{-}5}$, larger than expected from a calculation of dd¯ direct production but smaller than predicted by a simple coalescence model. We also report limits on the production of exotic particles.

Contrary to the conventional view of spherical nuclei as being chaotic in nature, we find, by means of level statistics, that some heavy nuclei exhibit deviations toward regularity unlike the predictions of the random matrix theory. We show that the degree of regularity is closely connected to the ratio of the nuclear size to the range of the nuclear force.

We have measured asymmetric photoelectron angular distributions for atomic rubidium. Ionization is induced by a one-photon interaction with 280 nm light and by a two-photon interaction with 560 nm light. Interference between the even- and odd-parity free-electron wave functions allows us to control the direction of maximum electron flux by varying the relative phase of the two laser fields.

A theory of electron capture from states of high principal quantum number n by multicharged ions is presented. We predict a capture cross section that depends upon the n of the initial state as ${\mathit{n}}^{\mathrm{\beta }}$ where β is as large as 7 in some cases. This surprisingly high n dependence explains why a small (less than 0.1%) fraction of hydrogen in high n states contributes 30% of the capture yield in ${\mathrm{O}}^{5+}$+H collisions. The theory also predicts a strong dependence on the dipole moment of the initial state.

We have investigated the properties of light emitted into the nearest subthreshold mode on either side of the single lasing mode of an argon-ion laser. This light beats with the laser line and hence contributes to the laser’s intensity-fluctuation noise spectrum over a range of frequencies centered close to the longitudinal mode separation. The noise contribution from one subthreshold mode is shown to be strongly anticorrelated with that from the other, leading to optical noise cancellation.