29 research outputs found
Criticality of the Mean-Field Spin-Boson Model: Boson State Truncation and Its Scaling Analysis
The spin-boson model has nontrivial quantum phase transitions at zero
temperature induced by the spin-boson coupling. The bosonic numerical
renormalization group (BNRG) study of the critical exponents and
of this model is hampered by the effects of boson Hilbert space
truncation. Here we analyze the mean-field spin boson model to figure out the
scaling behavior of magnetization under the cutoff of boson states . We
find that the truncation is a strong relevant operator with respect to the
Gaussian fixed point in and incurs the deviation of the exponents
from the classical values. The magnetization at zero bias near the critical
point is described by a generalized homogeneous function (GHF) of two variables
and . The universal function has a
double-power form and the powers are obtained analytically as well as
numerically. Similarly, is found to be a GHF of
and . In the regime , the truncation produces no effect.
Implications of these findings to the BNRG study are discussed.Comment: 9 pages, 7 figure
Precise atomic masses of neutron-rich Br and Rb nuclei close to the r-process path
The Penning trap mass spectrometer JYFLTRAP, coupled to the Ion-Guide Isotope Separator On-Line (IGISOL) facility at Jyvaskyla, was employed to measure the atomic masses of neutron rich 85 to 92Br and 94 to 97Rb isotopes with a typical accuracy less than 10 keV. Discrepancies with the older data are discussed. Comparison to different mass models is presented. Details of nuclear structure, shell and subshell closures are investigated by studying the two-neutron separation energy and the shell gap energy
Influences on the triple alpha process beyond the Hoyle state
The triple alpha process is studied using indirect methods. The beta decays of 12N and 12B are used to probe the triple alpha continuum of 12C. Different independent breakup channels are identified, consistently showing that the 10 MeV strength is dominated by a 0+ state interfering with the Hoyle state ghost. The 13.14 MeV region on the other hand is dominated by a 2+ state. Present: National Superconducting Cyclotron Laboratory, Michigan State University, East Lansing, Michigan MI-48824, USA.</p
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Differential predictors for alcohol use in adolescents as a function of familial risk
Abstract: Traditional models of future alcohol use in adolescents have used variable-centered approaches, predicting alcohol use from a set of variables across entire samples or populations. Following the proposition that predictive factors may vary in adolescents as a function of family history, we used a two-pronged approach by first defining clusters of familial risk, followed by prediction analyses within each cluster. Thus, for the first time in adolescents, we tested whether adolescents with a family history of drug abuse exhibit a set of predictors different from adolescents without a family history. We apply this approach to a genetic risk score and individual differences in personality, cognition, behavior (risk-taking and discounting) substance use behavior at age 14, life events, and functional brain imaging, to predict scores on the alcohol use disorders identification test (AUDIT) at age 14 and 16 in a sample of adolescents (N = 1659 at baseline, N = 1327 at follow-up) from the IMAGEN cohort, a longitudinal community-based cohort of adolescents. In the absence of familial risk (n = 616), individual differences in baseline drinking, personality measures (extraversion, negative thinking), discounting behaviors, life events, and ventral striatal activation during reward anticipation were significantly associated with future AUDIT scores, while the overall model explained 22% of the variance in future AUDIT. In the presence of familial risk (n = 711), drinking behavior at age 14, personality measures (extraversion, impulsivity), behavioral risk-taking, and life events were significantly associated with future AUDIT scores, explaining 20.1% of the overall variance. Results suggest that individual differences in personality, cognition, life events, brain function, and drinking behavior contribute differentially to the prediction of future alcohol misuse. This approach may inform more individualized preventive interventions
Differential predictors for alcohol use in adolescents as a function of familial risk
Abstract: Traditional models of future alcohol use in adolescents have used variable-centered approaches, predicting alcohol use from a set of variables across entire samples or populations. Following the proposition that predictive factors may vary in adolescents as a function of family history, we used a two-pronged approach by first defining clusters of familial risk, followed by prediction analyses within each cluster. Thus, for the first time in adolescents, we tested whether adolescents with a family history of drug abuse exhibit a set of predictors different from adolescents without a family history. We apply this approach to a genetic risk score and individual differences in personality, cognition, behavior (risk-taking and discounting) substance use behavior at age 14, life events, and functional brain imaging, to predict scores on the alcohol use disorders identification test (AUDIT) at age 14 and 16 in a sample of adolescents (N = 1659 at baseline, N = 1327 at follow-up) from the IMAGEN cohort, a longitudinal community-based cohort of adolescents. In the absence of familial risk (n = 616), individual differences in baseline drinking, personality measures (extraversion, negative thinking), discounting behaviors, life events, and ventral striatal activation during reward anticipation were significantly associated with future AUDIT scores, while the overall model explained 22% of the variance in future AUDIT. In the presence of familial risk (n = 711), drinking behavior at age 14, personality measures (extraversion, impulsivity), behavioral risk-taking, and life events were significantly associated with future AUDIT scores, explaining 20.1% of the overall variance. Results suggest that individual differences in personality, cognition, life events, brain function, and drinking behavior contribute differentially to the prediction of future alcohol misuse. This approach may inform more individualized preventive interventions
A new three-parameter H, G<sub>1</sub>, G<sub>2</sub> magnitude phase function for asteroids
International audienceWe have developed a new three-parameter H, G1, G2 magnitude phase function for asteroids. The phase function is aimed at replacing the currently adopted two-parameter H, G phase function. We show that H, G1, G2 produces better fits of available magnitude - phase curves of well-observed asteroids. We show also that the new system can be conveniently reduced to a two-parameter H, G12 magnitude phase function, which allows us to derive better estimates of the absolute magnitudes of asteroids for which poorly-sampled magnitude phase curves are available