1,186 research outputs found
Supersymmetry in the Standard Model
We prove that the bosons and massless fermions of one generation of the
standard model are supersymmetric partners of each other. Except for one
additional auxilliary vector boson, there are no other SUSY particles.Comment: RevTex, 6 pages, uuencoded tar compressed fil
New Renormalization Group Equations and the Naturalness Problem
Looking for an observable manifestation of the so-called unnaturalness of
scalar fields we introduce a seemingly new set of differential equations for
connected Green functions. These equations describe the momentum dependence of
the Green functions and are close relatives to the previously known
renormalization group equations. Applying the new equations to the theory of
scalar field with interaction we identify a relation between the
four-point Green function and the propagator which expresses the unnaturalness
of the scalar field. Possible manifestations of the unnaturalness at low
momenta are briefly discussed.Comment: 12 revtex pages; a coefficient has been corrected in eq. (34), four
new references added; final version to appear in Phys. Rev.
Off-Shell Scattering Amplitudes for WW Scattering and the Role of the Photon Pole
We derive analytic expressions for high energy off-shell scattering
amplitudes of weak vector bosons. They are obtained from six fermion final
states in processes of the type . As an application we reconsider the
unitarity bounds on the Higgs mass. Particular attention is given to the role
of the photon exchange which has not been considered in earlier investigations;
we find that the photon weakens the bound of the Higgs mass.Comment: 16 pages, 8 figure
An NMR study on internal browning in pears
Internal browning in pears (Pyrus communis L. cv. Blanquilla) has been studied by NMR and MRI in order to develop a non-destructive procedure for on-line disorder identification. For NMR relaxometry, disordered tissue shows higher transverse relaxation rates compared to sound tissue, especially at higher magnetic field strength and for long pulse spacing. Membrane alteration and therefore tissue disintegration, as well as water evaporation, appear to be the main causes of this response. Correlation between relaxation times and diffusion showed that the proton pools in disordered tissue are grouped into a smaller number of populations compared to sound tissue, also highlighting cell decompartmentation in disordered tissue. At a macroscopic level, fast low angle shot MR images, effective transverse relaxation-weighted (TR 11 ms and TE 3.7 ms) and proton density-weighted (TR 7.6 ms and TE 2.5 ms), were acquired for pears at a rate of 54 mm/s. Images have been discriminated for internal breakdown according to histogram characteristics. Up to 94 and 96% of pears, respectively, were correctly classified in the former and the latter type of images. In this study a minimum value of 12% of tissue affected by breakdown was always clearly identifie
Post-Wick theorems for symbolic manipulation of second-quantized expressions in atomic many-body perturbation theory
Manipulating expressions in many-body perturbation theory becomes unwieldily
with increasing order of the perturbation theory. Here I derive a set of
theorems for efficient simplification of such expressions. The derived rules
are specifically designed for implementing with symbolic algebra tools. As an
illustration, we count the numbers of Brueckner-Goldstone diagrams in the first
several orders of many-body perturbation theory for matrix elements between two
states of a mono-valent system.Comment: J. Phys. B. (in press); Mathematica packages available from
http://wolfweb.unr.edu/homepage/andrei/WWW-tap/mathematica.htm
Leading quantum gravitational corrections to QED
We consider the leading post-Newtonian and quantum corrections to the
non-relativistic scattering amplitude of charged spin-1/2 fermions in the
combined theory of general relativity and QED. The coupled Dirac-Einstein
system is treated as an effective field theory. This allows for a consistent
quantization of the gravitational field. The appropriate vertex rules are
extracted from the action, and the non-analytic contributions to the 1-loop
scattering matrix are calculated in the non-relativistic limit. The
non-analytical parts of the scattering amplitude are known to give the long
range, low energy, leading quantum corrections, are used to construct the
leading post-Newtonian and quantum corrections to the two-particle
non-relativistic scattering matrix potential for two massive fermions with
electric charge.Comment: 14 pages, 29 figures, format RevTex
Brain structural abnormalities in obesity: relation to age, genetic risk, and common psychiatric disorders:Evidence through univariate and multivariate mega-analysis including 6420 participants from the ENIGMA MDD working group
Brain structural abnormalities in obesity: relation to age, genetic risk, and common psychiatric disorders:Evidence through univariate and multivariate mega-analysis including 6420 participants from the ENIGMA MDD working group
Heavy Fermion Screening Effects and Gauge Invariance
We show that the naively expected large virtual heavy fermion effects in low
energy processes may be screened if the process under consideration contains
external gauge bosons constrained by gauge invariance. We illustrate this by a
typical example of the process . Phenomenological
implications are also briefly indicated.Comment: a miss-print fixed, 7 pages, LaTex, no figure
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