2,442 research outputs found
Kinetic Regimes and Cross-Over Times in Many-Particle Reacting Systems
We study kinetics of single species reactions ("A+A -> 0") for general local
reactivity Q and dynamical exponent z (rms displacement x_t ~ t^{1/z}.) For
small molecules z=2, whilst z=4,8 for certain polymer systems. For dimensions d
above the critical value d_c=z, kinetics are always mean field (MF). Below d_c,
the density n_t initially follows MF decay, n_0 - n_t ~ n_0^2 Q t. A 2-body
diffusion-controlled regime follows for strongly reactive systems (Q>Qstar ~
n_0^{(z-d)/d}) with n_0 - n_t ~ n_0^2 x_t^d. For Q<Qstar, MF kinetics persist,
with n_t ~ 1/Qt. In all cases n_t ~ 1/x_t^d at the longest times. Our analysis
avoids decoupling approximations by instead postulating weak physically
motivated bounds on correlation functions.Comment: 10 pages, 1 figure, uses bulk2.sty, minor changes, submitted to
Europhysics Letter
Virtual effects of light gauginos and higgsinos: a precision electroweak analysis of split supersymmetry
We compute corrections to precision electroweak observables in supersymmetry
in the limit that scalar superpartners are very massive and decoupled. This
leaves charginos and neutralinos and a Standard Model-like Higgs boson as the
only states with unknown mass substantially affecting the analysis. We give
complete formulas for the chargino and neutralino contributions, derive simple
analytic results for the pure gaugino and higgsino cases, and study the general
case. We find that in all circumstances, the precision electroweak fit improves
when the charginos and neutralinos are near the current direct limits. Larger
higgsino and gaugino masses worsen the fit as the theory predictions
asymptotically approach those of the Standard Model. Since the Standard Model
is considered by most to be an adequate fit to the precision electroweak data,
an important corollary to our analysis is that all regions of parameter space
allowed by direct collider constraints are also allowed by precision
electroweak constraints in split supersymmetry.Comment: 22 pages, 5 figures, v2: typos fixed and note adde
Reactive dynamics on fractal sets: anomalous fluctuations and memory effects
We study the effect of fractal initial conditions in closed reactive systems
in the cases of both mobile and immobile reactants. For the reaction , in the absence of diffusion, the mean number of particles is shown to
decay exponentially to a steady state which depends on the details of the
initial conditions. The nature of this dependence is demonstrated both
analytically and numerically. In contrast, when diffusion is incorporated, it
is shown that the mean number of particles decays asymptotically as
, the memory of the initial conditions being now carried by the
dynamical power law exponent. The latter is fully determined by the fractal
dimension of the initial conditions.Comment: 7 pages, 2 figures, uses epl.cl
The metallic transport of (TMTSF)_2X organic conductors close to the superconducting phase
Comparing resistivity data of quasi-one dimensional superconductors
(TMTSF)_2PF_6 and (TMTSF)_2ClO_4 along the least conducting c*-axis and along
the high conductivity a -axis as a function of temperature and pressure, a low
temperature regime is observed in which a unique scattering time governs
transport along both directions of these anisotropic conductors. However, the
pressure dependence of the anisotropy implies a large pressure dependence of
the interlayer coupling. This is in agreement with the results of
first-principles DFT calculations implying methyl group hyperconjugation in the
TMTSF molecule. In this low temperature regime, both materials exhibit for rc a
temperature dependence aT + bT^2. Taking into account the strong pressure
dependence of the anisotropy, the T-linear rc is found to correlate with the
suppression of the superconducting Tc, in close analogy with ra data. This work
is revealing the domain of existence of the 3D coherent regime in the generic
(TMTSF)_2X phase diagram and provides further support for the correlation
between T-linear resistivity and superconductivity in non-conventional
superconductors
Photonic SUSY Two-Loop Corrections to the Muon Magnetic Moment
Photonic SUSY two-loop corrections to the muon magnetic moment are
contributions from diagrams where an additional photon loop is attached to a
SUSY one-loop diagram. These photonic corrections are evaluated exactly,
extending a leading-log calculation by Degrassi and Giudice. Compact analytical
expressions are provided and the numerical behaviour is discussed. The photonic
corrections reduce the SUSY one-loop result by 7...9%. The new terms are
typically around ten times smaller than the leading logarithms, but they can be
larger and have either sign in cases with large SUSY mass splittings. We also
provide details on renormalization and regularization and on how to incorporate
the photonic corrections into a full SUSY two-loop calculation.Comment: 25 page
Advances towards reliable identification and concentration determination of rare cells in peripheral blood
Through further development, integration and validation of micro-nano-bio and biophotonics systems FP7 CanDo is developing an instrument that will permit highly reproducible and reliable identification and concentration determination of rare cells in peripheral blood for two key societal challenges, early and low cost anti-cancer drug efficacy determination and cancer diagnosis/monitoring. A cellular link between the primary malignant tumour and the peripheral metastases, responsible for 90% of cancerrelated deaths, has been established in the form of circulating tumour cells (CTCs) in peripheral blood. Furthermore, the relatively short survival time of CTCs in peripheral blood means that their detection is indicative of tumour progression thereby providing in addition to a prognostic value an evaluation of therapeutic efficacy and early recognition of tumour progression in theranostics. In cancer patients however blood concentrations are very low (=1 CTC/1E9 cells) and current detection strategies are too insensitive, limiting use to prognosis of only those with advanced metastatic cancer. Similarly, problems occur in therapeutics with anti-cancer drug development leading to lengthy and costly trials often preventing access to market. The novel cell separation/Raman analysis technologies plus nucleic acid based molecular characterization of the CanDo platform will provide an accurate CTC count with high throughput and high yield meeting both key societal challenges. Being beyond the state of art it will lead to substantial share gains not just in the high end markets of drug discovery and cancer diagnostics but due to modular technologies also in others. Here we present preliminary DNA hybridization sensing results
A mathematical programming tool for an efficient decision-making on teaching assignment under non-regular time schedules
[EN] In this paper, an optimization tool based on a MILP model to support the teaching assignment process is proposed. It considers not only hierarchical issues among lecturers but also their preferences to teach a particular subject, the non-regular time schedules throughout the academic year, different type of credits, number of groups and other specific characteristics. Besides, it adds restrictions based on the time compatibility among the different subjects, the lecturers' availability, the maximum number of subjects per lecturer, the maximum number of lecturers per subject as well as the maximum and minimum saturation level for each lecturer, all of them in order to increase the teaching quality. Schedules heterogeneity and other features regarding the operation of some universities justify the usefulness of this model since no study that deals with all of them has been found in the literature review. Model validation has been performed with two real data sets collected from one academic year schedule at the Spanish University Universitat Politecnica de Valencia.Solano Cutillas, P.; Pérez Perales, D.; Alemany Díaz, MDM. (2022). A mathematical programming tool for an efficient decision-making on teaching assignment under non-regular time schedules. Operational Research. 22(3):2899-2942. https://doi.org/10.1007/s12351-021-00638-12899294222
Recent progress on isospin breaking corrections and their impact on the muon g-2 value
We describe some recent results on isospin breaking corrections which are of
relevance for predictions of the leading order hadronic contribution to the
muon anomalous magnetic moment (amuhadLO) when using tau lepton data. When
these corrections are applied to the new combined data on the pi^+pi^0 spectral
function, the prediction for amuhadLO based on tau lepton data gets closer to
the one obtained using e^+e^- data.Comment: 6 pages, 3 figures, Proceedings of the PhiPsi09 Workshop, Oct. 13-16,
2009, Beijing, China. Some typos corrected, and the FSR correction used in a
previous work is added to Table
Bounds on the attractor dimension for magnetohydrodynamic channel flow with parallel magnetic field at low magnetic Reynolds number
We investigate aspects of low-magnetic-Reynolds-number flow between two
parallel, perfectly insulating walls, in the presence of an imposed magnetic
field parallel to the bounding walls. We find a functional basis to describe
the flow, well adapted to the problem of finding the attractor dimension, and
which is also used in subsequent direct numerical simulation of these flows.
For given Reynolds and Hartmann numbers, we obtain an upper bound for the
dimension of the attractor by means of known bounds on the nonlinear inertial
term and this functional basis for the flow. Three distinct flow regimes
emerge: a quasi-isotropic 3D flow, a non-isotropic three-dimensional (3D) flow,
and a 2D flow. We find the transition curves between these regimes in the space
parameterized by Hartmann number Ha and attractor dimension . We
find how the attractor dimension scales as a function of Reynolds and Hartmann
numbers (Re and Ha) in each regime. We also investigate the thickness of the
boundary layer along the bounding wall, and find that in all regimes this
scales as 1/Re, independently of the value of Ha, unlike Hartmann boundary
layers found when the field is normal to the channel. The structure of the set
of least dissipative modes is indeed quite different between these two cases
but the properties of turbulence far from the walls (smallest scales and number
of degrees of freedom) are found to be very similar
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