Search results for "Metas"
showing 10 items of 1693 documents
Spin glasses: Experimental facts, theoretical concepts, and open questions
1986
This review summarizes recent developments in the theory of spin glasses, as well as pertinent experimental data. The most characteristic properties of spin glass systems are described, and related phenomena in other glassy systems (dielectric and orientational glasses) are mentioned. The Edwards-Anderson model of spin glasses and its treatment within the replica method and mean-field theory are outlined, and concepts such as "frustration," "broken replica symmetry," "broken ergodicity," etc., are discussed. The dynamic approach to describing the spin glass transition is emphasized. Monte Carlo simulations of spin glasses and the insight gained by them are described. Other topics discussed …
3He neutron spin filter at ILL
1997
Abstract The strongly spin-dependent absorption of neutrons in nuclear spin polarized 3He opens the possibility to polarize neutrons over the full-spectrum of cold, thermal and epithermal neutrons. At ILL a neutron spin filter (NSF) development started which uses the direct optical pumping of metastable 3He atoms in a 3He plasma at 1 mbar. At present 0.5 bar 1 of gaseous 3He can be polarized within 1 h. Subsequent polarization-preserving compression by a two-stage compressor system enables one to prepare NSF cells of about 300 cm3 volume in the required pressure range of several bars. A remote type of operation based on relaxation times of up to 100 h has been demonstrated in a first survey…
Dynamics of wetting transitions: A time-dependent Ginzburg-Landau treatment
1987
The dynamic behavior at wetting transitions is studied for systems with short-range forces and nonconserved order parameter. From a continuum limit of a purely relaxational lattice model in mean-field approximation, a time-dependent Ginzburg-Landau equation with a time-dependent boundary condition at the surface is derived in the long wavelength approximation. The dynamics of relaxation close to stable and metastable states is treated in linear response. A divergence of the relaxation time occurs both for critical wetting and along the surface spinodal lines (in the case of first-order wetting), although the static surface layer susceptibilities χ1, χ11 stay finite at the surface spinodal i…
Enhancement of stability in randomly switching potential with metastable state
2004
The overdamped motion of a Brownian particle in randomly switching piece-wise metastable linear potential shows noise enhanced stability (NES): the noise stabilizes the metastable system and the system remains in this state for a longer time than in the absence of white noise. The mean first passage time (MFPT) has a maximum at a finite value of white noise intensity. The analytical expression of MFPT in terms of the white noise intensity, the parameters of the potential barrier, and of the dichotomous noise is derived. The conditions for the NES phenomenon and the parameter region where the effect can be observed are obtained. The mean first passage time behaviours as a function of the mea…
Crystallization of hard spheres revisited. I. Extracting kinetics and free energy landscape from forward flux sampling
2018
We investigate the kinetics and the free energy landscape of the crystallization of hard spheres from a supersaturated metastable liquid though direct simulations and forward flux sampling. In this first paper, we describe and test two different ways to reconstruct the free energy barriers from the sampled steady state probability distribution of cluster sizes without sampling the equilibrium distribution. The first method is based on mean first passage times, and the second method is based on splitting probabilities. We verify both methods for a single particle moving in a double-well potential. For the nucleation of hard spheres, these methods allow us to probe a wide range of supersatura…
Evidence for metastable photo-induced superconductivity in K3C60
2021
Far and mid infrared optical pulses have been shown to induce non-equilibrium unconventional orders in complex materials, including photo-induced ferroelectricity in quantum paraelectrics, magnetic polarization in antiferromagnets and transient superconducting correlations in the normal state of cuprates and organic conductors. In the case of non-equilibrium superconductivity, femtosecond drives have generally resulted in electronic properties that disappear immediately after excitation, evidencing a state that lacks intrinsic rigidity. Here, we make use of a new optical device to drive metallic K$_3$C$_{60}$ with mid-infrared pulses of tunable duration, ranging between one picosecond and o…
Doppler free ?dark resonances? for hyperfine measurements and isotope shifts in Ca+ isotopes in a Paul trap
1995
We have observed “dark resonances” in theA-type level structure, formed by the 4S1/2 ground state, the 4P1/2 excited state and the low lying metastable 3D3/2 state in the Calcium ion, confined in a Paul radio-frequency trap. These Doppler-free and potentially very narrow resonances were used to determine the magnetic dipole hyperfine interaction constant A for the 4P1/2 and 3D3/2 state of43Ca+, giving −142(8) MHz and −48.3(1.6) MHz, respectively. From measurements of the P-D (E1) and S-D (E2) transition wavelength in a mixture of43Ca+ and40Ca+ we determined the isotope shifts of these lines.
Metastability of Traffic Flow in Zero-Range Model
2007
The development of traffic jams in vehicular flow is an everyday example of the occurence of phase separation in low-dimensional driven systems, a topic which has attracted much recent interest [1–4]. In [5] the existence of phase separation is related to the size-dependence of domain currents and a quantitative criterion is obtained by considering the zero-range process (ZRP) as a generic model for domain dynamics. We use zero-range picture to study the phase separation in traffic flow in the spirit of the probabilistic (master equation) description of transportation [6]. Significantly, we find [7] that prior to condensation studied in previous works [8, 9] the system can exist in a homoge…
Numerical simulations and exactly soluble spin-glass models.
1985
Some general arguments based on recent numerical work are presented to explain the different behavior of short-range, random-bond and long-range, random-site spin glasses. We then analyze an exactly soluble spin-glass model, which may be solved without replicas, and show that, except for the absence of microscopic metastable states, its main features are consistent with the long-range picture.
ExperimentalgJfactor in the metastable 5D3/2level ofBa+
1996
The Zeeman splitting of the metastable 5${\mathit{D}}_{3/2}$ level of $^{138}\mathrm{Ba}^{+}$ in a magnetic field of 6 T has been measured in a laser-microwave double resonance experiment in a Penning ion trap. The magnetic field at the ion's position is determined by the cyclotron frequency of electrons stored in the same trap. From the ratio of both transition frequencies we obtain a ${\mathit{g}}_{\mathit{J}}$ value of 0.799 327 8(3). As a by-product, we confirmed earlier measurements on the 6${\mathit{S}}_{1/2}$ ground-state ${\mathit{g}}_{\mathit{J}}$ factor to 2.002 492 2(10). The precision in both experiments is sufficient to test relativistic many-body calculations. \textcopyright{}…