7,413 research outputs found
Motional Broadening in Ensembles With Heavy-Tail Frequency Distribution
We show that the spectrum of an ensemble of two-level systems can be
broadened through `resetting' discrete fluctuations, in contrast to the
well-known motional-narrowing effect. We establish that the condition for the
onset of motional broadening is that the ensemble frequency distribution has
heavy tails with a diverging first moment. We find that the asymptotic
motional-broadened lineshape is a Lorentzian, and derive an expression for its
width. We explain why motional broadening persists up to some fluctuation rate,
even when there is a physical upper cutoff to the frequency distribution.Comment: 6 pages, 4 figure
Mode signature and stability for a Hamiltonian model of electron temperature gradient turbulence
Stability properties and mode signature for equilibria of a model of electron
temperature gradient (ETG) driven turbulence are investigated by Hamiltonian
techniques. After deriving the infinite families of Casimir invariants,
associated with the noncanonical Poisson bracket of the model, a sufficient
condition for stability is obtained by means of the Energy-Casimir method. Mode
signature is then investigated for linear motions about homogeneous equilibria.
Depending on the sign of the equilibrium "translated" pressure gradient, stable
equilibria can either be energy stable, i.e.\ possess definite linearized
perturbation energy (Hamiltonian), or spectrally stable with the existence of
negative energy modes (NEMs). The ETG instability is then shown to arise
through a Kre\u{\i}n-type bifurcation, due to the merging of a positive and a
negative energy mode, corresponding to two modified drift waves admitted by the
system. The Hamiltonian of the linearized system is then explicitly transformed
into normal form, which unambiguously defines mode signature. In particular,
the fast mode turns out to always be a positive energy mode (PEM), whereas the
energy of the slow mode can have either positive or negative sign
An importance sampling algorithm for generating exact eigenstates of the nuclear Hamiltonian
We endow a recently devised algorithm for generating exact eigensolutions of
large matrices with an importance sampling, which is in control of the extent
and accuracy of the truncation of their dimensions. We made several tests on
typical nuclei using a correlated basis obtained from partitioning the shell
model space. The sampling so implemented allows not only for a substantial
reduction of the shell model space but also for an extrapolation to exact
eigenvalues and E2 strengths.Comment: A compressed file composed of a text in latex of 19 pages and 9
figures in p
Parametrization of the octupole degrees of freedom
A simple parametrization for the octupole collective variables is proposed
and the symmetries of the wave functions are discussed in terms of the
solutions corresponding to the vibrational limit. [PACS: 21.60Ev, 21.60.Fw,
21.10.Re]Comment: 14 page
Observable Electron EDM and Leptogenesis
In the context of the minimal supersymmetric seesaw model, the CP-violating
neutrino Yukawa couplings might induce an electron EDM. The same interactions
may also be responsible for the generation of the observed baryon asymmetry of
the Universe via leptogenesis. We identify in a model-independent way those
patterns within the seesaw models which predict an electron EDM at a level
probed by planned laboratory experiments and show that negative searches on
\tau-> e \gamma decay may provide the strongest upper bound on the electron
EDM. We also conclude that a possible future detection of the electron EDM is
incompatible with thermal leptogenesis, even when flavour effects are accounted
for.Comment: 26 pages, 6 figure
Approximate square-root-time relaxation in glass-forming liquids
We present data for the dielectric relaxation of 43 glass-forming organic
liquids, showing that the primary (alpha) relaxation is often close to
square-root-time relaxation. The better an inverse power-law description of the
high-frequency loss applies, the more accurately is square-root-time relaxation
obeyed. These findings suggest that square-root-time relaxation is generic to
the alpha process, once a common view, but since long believed to be incorrect.
Only liquids with very large dielectric losses deviate from this picture by
having consistently narrower loss peaks. As a further challenge to the
prevailing opinion, we find that liquids with accurate square-root-time
relaxation cover a wide range of fragilities
Reconstructing Seesaws
We explore some aspects of "reconstructing" the heavy singlet sector of
supersymmetric type I seesaw models, for two, three or four singlets. We work
in the limit where one light neutrino is massless. In an ideal world, where
selected coefficients of the TeV-scale effective Lagrangian could be measured
with arbitrary accuracy, the two-singlet case can be reconstructed, two three
or more singlets can be differentiated, and an inverse seesaw with four
singlets can be reconstructed. In a more realistic world, we estimate \ell_\a
\to \ell_\b \gamma expectations with a "Minimal-Flavour-Violation-like"
ansatz, which gives a relation between ratios of the three branching ratios.
The two singlet model predicts a discrete set of ratios.Comment: 14 page
Relativistic Turbulence: A Long Way from Preheating to Equilibrium
We study, both numerically and analytically, the development of equilibrium
after preheating. We show that the process is characterised by the appearance
of Kolmogorov spectra and the evolution towards thermal equilibrium follows
self-similar dynamics. Simplified kinetic theory gives values for all
characteristic exponents which are close to what is observed in lattice
simulations. The resulting time for thermalization is long, and temperature at
thermalization is low, eV in the simple
inflationary model. Our results allow a straightforward generalization to
realistic models.Comment: 4 pages, 3figures, LaTe
Behavioral economics implementation: Regret lottery improves mHealth patient study adherence.
Background: Nonadherence to study protocols reduces the generalizability, validity, and statistical power of longitudinal studies.
Purpose: To determine whether an automated electronically-delivered regret lottery would improve adherence to an intensive mHealth self-monitoring protocol as part of a longitudinal observational study.
Methods: We enrolled 77 adults into a 52-week study requiring five daily ecologic momentary assessments (EMA) of stress and daily accelerometer use. We performed a pre/post single-arm study to evaluate the efficacy of a lottery intervention in improving adherence to this protocol. Midway through the study, participants were invited to enter a weekly regret lottery ($50 prize, expected value
Results: 62 participants consented to lottery participation. In the 12 weeks prior to lottery initiation, weekly adherence was declining (slope -1.4%/week). The weekly per-participant probability of adherence was higher after lottery initiation when comparing the 4-week (32% pre-lottery vs 50% post-lottery, p \u3c 0.001), 8-week (37% vs 49%, p \u3c 0.001), and 12-week periods (39% vs 45%, p = 0.001) before and after lottery initiation. However, the rate of decline in adherence over time was unchanged.
Conclusion: The implementation of an automated, electronically-delivered weekly regret lottery improved adherence with an intensive self-monitoring study protocol. Regret lotteries may represent a cost-effective tool to improve adherence and reduce bias caused by dropout or nonadherence
Tribimaximal Neutrino Mixing and a Relation Between Neutrino- and Charged Lepton-Mass Spectra
Brannen has recently pointed out that the observed charged lepton masses
satisfy the relation m_e +m_\mu +m_\tau = {2/3}
(\sqrt{m_e}+\sqrt{m_\mu}+\sqrt{m_\tau})^2, while the observed neutrino masses
satisfy the relation m_{\nu 1} +m_{\nu 2} +m_{\nu 3} = {2/3} (-\sqrt{m_{\nu
1}}+\sqrt{m_{\nu 2}}+\sqrt{m_{\nu 3}})^2. It is discussed what neutrino Yukawa
interaction form is favorable if we take the fact pointed out by Brannen
seriously.Comment: 13 pages, presentation modifie
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