1,093 research outputs found
UV frequency metrology on CO (a3Pi); isotope effects and sensitivity to a variation of the proton-to-electron mass ratio
UV frequency metrology has been performed on the a3Pi - X1Sigma+ (0,0) band
of various isotopologues of CO using a frequency-quadrupled injection-seeded
narrow-band pulsed Titanium:Sapphire laser referenced to a frequency comb
laser. The band origin is determined with an accuracy of 5 MHz (delta \nu / \nu
= 3 * 10^-9), while the energy differences between rotational levels in the
a3Pi state are determined with an accuracy of 500 kHz. From these measurements,
in combination with previously published radiofrequency and microwave data, a
new set of molecular constants is obtained that describes the level structure
of the a3Pi state of 12C16O and 13C16O with improved accuracy. Transitions in
the different isotopologues are well reproduced by scaling the molecular
constants of 12C16O via the common mass-scaling rules. Only the value of the
band origin could not be scaled, indicative of a breakdown of the
Born-Oppenheimer approximation. Our analysis confirms the extreme sensitivity
of two-photon microwave transitions between nearly-degenerate rotational levels
of different Omega-manifolds for probing a possible variation of the
proton-to-electron mass ratio, \mu=m_p/m_e, on a laboratory time scale
Conformal Anomaly and Critical Exponents of the XY-Ising Model
We use extensive Monte Carlo transfer matrix calculations on infinite strips
of widths up to 30 lattice spacing and a finite-size scaling analysis to
obtain critical exponents and conformal anomaly number for the
two-dimensional -Ising model. This model is expected to describe the
critical behavior of a class of systems with simultaneous and
symmetries of which the fully frustrated model is a special case. The
effective values obtained for show a significant decrease with at
different points along the line where the transition to the ordered phase takes
place in a single transition. Extrapolations based on power-law corrections
give values consistent with although larger values can not be ruled
out. Critical exponents are obtained more accurately and are consistent with
previous Monte Carlo simulations suggesting new critical behavior and with
recent calculations for the frustrated model.Comment: 33 pages, 13 latex figures, uses RevTeX 3.
Crossover Scaling Functions in One Dimensional Dynamic Growth Models
The crossover from Edwards-Wilkinson () to KPZ () type growth is
studied for the BCSOS model. We calculate the exact numerical values for the
and massgap for using the master equation. We predict
the structure of the crossover scaling function and confirm numerically that
and , with . KPZ type growth is
equivalent to a phase transition in meso-scopic metallic rings where attractive
interactions destroy the persistent current; and to endpoints of facet-ridges
in equilibrium crystal shapes.Comment: 11 pages, TeX, figures upon reques
Roughening Induced Deconstruction in (100) Facets of CsCl Type Crystals
The staggered 6-vertex model describes the competition between surface
roughening and reconstruction in (100) facets of CsCl type crystals. Its phase
diagram does not have the expected generic structure, due to the presence of a
fully-packed loop-gas line. We prove that the reconstruction and roughening
transitions cannot cross nor merge with this loop-gas line if these degrees of
freedom interact weakly. However, our numerical finite size scaling analysis
shows that the two critical lines merge along the loop-gas line, with strong
coupling scaling properties. The central charge is much larger than 1.5 and
roughening takes place at a surface roughness much larger than the conventional
universal value. It seems that additional fluctuations become critical
simultaneously.Comment: 31 pages, 9 figure
Pacing as a strategy to improve energy management in myalgic encephalomyelitis/chronic fatigue syndrome: a consensus document
Purpose: Myalgic encephalomyelitis/chronic fatigue syndrome (ME/CFS) is a debilitating condition characterized by a number of symptoms which typically worsen following minimal exertion. Various strategies to manage the limited energy levels have been proposed. Of these, pacing has been consistently rated as one of the most helpful in surveys conducted by patient groups. This review is a response to the paucity of the information on pacing in the scientific literature. Method: We describe the principle of pacing and how this can be adapted to meet individual abilities and preferences. A critical evaluation of the research was conducted to ascertain the benefits and limitations of this strategy. Results: Based on various studies, it is proposed that pacing can help to stabilize the condition and avoid post-exertional malaise. Conclusion: Pacing offers practitioners an additional therapeutic option which is acceptable to the majority of patients and can reduce the severity of the exertion-related symptoms of ME/CFS
Crossover from Isotropic to Directed Percolation
Directed percolation is one of the generic universality classes for dynamic
processes. We study the crossover from isotropic to directed percolation by
representing the combined problem as a random cluster model, with a parameter
controlling the spontaneous birth of new forest fires. We obtain the exact
crossover exponent at using Coulomb gas methods in 2D.
Isotropic percolation is stable, as is confirmed by numerical finite-size
scaling results. For , the stability seems to change. An intuitive
argument, however, suggests that directed percolation at is unstable and
that the scaling properties of forest fires at intermediate values of are
in the same universality class as isotropic percolation, not only in 2D, but in
all dimensions.Comment: 4 pages, REVTeX, 4 epsf-emedded postscript figure
Nonlinear sigma model study of a frustrated spin ladder
A model of two-leg spin-S ladder with two additional frustrating diagonal
exchange couplings J_{D}, J_{D}' is studied within the framework of the
nonlinear sigma model approach. The phase diagram has a rich structure and
contains 2S gapless phase boundaries which split off the boundary to the fully
saturated ferromagnetic phase when J_{D} and J_{D}' become different. For the
S=1/2 case, the phase boundaries are identified as separating two topologically
distinct Haldane-type phases discussed recently by Kim et al.
(cond-mat/9910023).Comment: revtex 4 pages, figures embedded (psfig
Increased Attention and Memory for Beloved-Related Information During Infatuation: Behavioral and Electrophysiological Data
Emotionally salient information is well attended and remembered. It has been shown that infatuated individuals have increased attention for their beloved. It is unknown whether this attention bias generalizes to information related to the beloved. Moreover, infatuated individuals report to remember trivial things about their beloved, but this has not yet been tested empirically. In two studies, we tested whether infatuated individuals have increased attention and memory for beloved-related information. In a passive viewing task (Study 1), the late positive potential, an event-related potential (ERP) component reflecting motivated attention, was enhanced for beloved-related vs friend-related words/phrases. In a recognition task (Study 2), memory performance and the frontal and parietal ERP old/new effects, reflecting familiarity and recollection, respectively, were not enhanced for beloved-related compared with friend-related words/phrases. In free recall tasks in both studies, memory was better for beloved-related than friend-related words/phrases. This research reveals that attention and memory are enhanced for beloved-related information. These attention and memory biases for beloved-related information were not due to valence, semantic relatedness, or experience, but to arousal. To conclude, romantic love has profound effects on cognition that play a clear role in daily life
Critical Exponents of the Four-State Potts Model
The critical exponents of the four-state Potts model are directly derived
from the exact expressions for the latent heat, the spontaneous magnetization,
and the correlation length at the transition temperature of the model.Comment: LaTex, 7 page
Temperature Dependence of Facet Ridges in Crystal Surfaces
The equilibrium crystal shape of a body-centered solid-on-solid (BCSOS) model
on a honeycomb lattice is studied numerically. We focus on the facet ridge
endpoints (FRE). These points are equivalent to one dimensional KPZ-type growth
in the exactly soluble square lattice BCSOS model. In our more general context
the transfer matrix is not stochastic at the FRE points, and a more complex
structure develops. We observe ridge lines sticking into the rough phase where
thesurface orientation jumps inside the rounded part of the crystal. Moreover,
the rough-to-faceted edges become first-order with a jump in surface
orientation, between the FRE point and Pokrovsky-Talapov (PT) type critical
endpoints. The latter display anisotropic scaling with exponent instead
of familiar PT value .Comment: 12 pages, 19 figure
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