1,437 research outputs found
Higgs inflation: consistency and generalisations
We analyse the self-consistency of inflation in the Standard Model, where the
Higgs field has a large non-minimal coupling to gravity. We determine the
domain of energies in which this model represents a valid effective field
theory as a function of the background Higgs field. This domain is bounded
above by the cutoff scale which is found to be higher than the relevant
dynamical scales throughout the whole history of the Universe, including the
inflationary epoch and reheating. We present a systematic scheme to take into
account quantum loop corrections to the inflationary calculations within the
framework of effective field theory. We discuss the additional assumptions that
must be satisfied by the ultra-violet completion of the theory to allow
connection between the parameters of the inflationary effective theory and
those describing the low-energy physics relevant for the collider experiments.
A class of generalisations of inflationary theories with similar properties is
constructed.Comment: 25 pages, 1 figur
The Polarization and the Recombination Mechanism
We use the recombination and the Thomas Precession Model to obtain a
prediction for the polarization in the
reaction. We study the effect of the recombination function on the
polarization.Comment: 4 pages, LaTex, 1 figures included, aipproc.sty included. Talk
presented at Simposio Latino Americano de Fisica de Altas Energias, Merida,
Mexico, November 199
Liesegang patterns : Studies on the width law
The so-called "width law" for Liesegang patterns, which states that the
positions x_n and widths w_n of bands verify the relation x_n \sim w_n^{\alpha}
for some \alpha>0, is investigated both experimentally and theoretically. We
provide experimental data exhibiting good evidence for values of \alpha close
to 1. The value \alpha=1 is supported by theoretical arguments based on a
generic model of reaction-diffusion.Comment: 7 pages, RevTeX, two columns, 5 figure
Low-threshold calcium spike bursts in the human thalamus: Common physiopathology for sensory, motor and limbic positive symptoms
Positive symptoms arise after lesions of the nervous system. They include neurogenic pain, tinnitus, abnormal movements, epilepsy and certain neuropsychiatric disorders. Stereotactic medial thalamotomies were performed on 104 patients with chronic therapy-resistant positive symptoms. Peroperative recordings of 2012 single units revealed an overwhelming unresponsiveness (99%) to sensory stimuli or motor activation. Among these unresponsive cells, 45.1% presented a rhythmic or random bursting activity. Rhythmic bursting activities had an average interburst interval of 263±46 ms corresponding to a frequency of 3.8±0.7 Hz. Frequency variations among the different symptoms were not statistically different. Intraburst characteristics such as the highest frequency encountered in the burst (480±80 Hz) or the mean frequency of the burst (206±44 Hz) were also similar in all patients. All bursts, rhythmic or random, fulfilled the extracellular criteria of low-threshold calcium spike (LTS) bursts. After medial thalamotomy and depending on the symptom, 43-67% of the patients reached a 50-100% relief, with sparing of all neurological functions. On the basis of these electrophysiological and clinical results, we propose a unified concept for all positive symptoms centred on a self-perpetuating thalamic cell membrane hyperpolarization, similar to the one seen in slow-wave slee
Derivation of the Matalon-Packter law for Liesegang patterns
Theoretical models of the Liesegang phenomena are studied and simple
expressions for the spacing coefficients characterizing the patterns are
derived. The emphasis is on displaying the explicit dependences on the
concentrations of the inner- and the outer-electrolytes. Competing theories
(ion-product supersaturation, nucleation and droplet growth, induced sol-
coagulation) are treated with the aim of finding the distinguishing features of
the theories. The predictions are compared with experiments and the results
suggest that the induced sol-coagulation theory is the best candidate for
describing the experimental observations embodied in the Matalon-Packter law.Comment: 9 pages, 7 figures, RevTe
Formation of Liesegang patterns: Simulations using a kinetic Ising model
A kinetic Ising model description of Liesegang phenomena is studied using
Monte Carlo simulations. The model takes into account thermal fluctuations,
contains noise in the chemical reactions, and its control parameters are
experimentally accessible. We find that noisy, irregular precipitation takes
place in dimension d=2 while, depending on the values of the control
parameters, either irregular patterns or precipitation bands satisfying the
regular spacing law emerge in d=3.Comment: 7 pages, 8 ps figures, RevTe
Low wave-functions of pions and kaons and their parton distribution functions
We study the low wave-functions of pions and kaons as an expansion in
terms of hadron-like Fock state fluctuations. In this formalism, pion and kaon
wave-functions are related one another. Consequently, the knowledge of the pion
structure allows the determination of parton distributions in kaons. In
addition, we show that the intrinsic (low ) sea of pions and kaons are
different due to their different valence quark structure. Finally, we analize
the feasibility of a method to extract kaon's parton distribution functions
within this approach and compare with available experimental data.Comment: 13 pages, 3 postscript figures include
Gluon distributions in nucleons and pions at a low resolution scale
In this paper we study the gluon distribution functions in nucleons and pions
at a low resolution scale. This is an important issue since parton
densities at low have always been taken as an external input which is
adjusted through DGLAP evolution to fit the experimental data at higher scales.
Here, in the framework of a model recently developed, it is shown that the
hypothetical cloud of {\it neutral} pions surrounding nucleons and pions
appears to be responsible for the characteristic valence-like gluon
distributions needed at the inital low scale. As an additional result, we get
the remarkable prediction that neutral and charged pions have different
intrinsic sea flavor contents.Comment: final version to appear in Phys. Rev. D. Discussion on several points
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