998 research outputs found
Balmer-Like Series for Baryon Resonances
The pole positions of various baryon resonances have been found to reveal a
well pronounced clustering, the so-called H"ohler cluster. In a previous work,
the H"ohler clusters have been shown to be identical to Lorentz multiplets of
the type (1/2+l', 1/2+l')*[(1/2,0)+(0,1/2)] with l' integer. Here we show that
the cluster positions are well described by means of a Balmer-series like
recursive mass formula.Comment: 5 pages LaTex, World Scientific style, two tables. A missing additive
factor of +1 on the rhs of Eq. (2) has been inserted and thereby a misprint,
not an error, correcte
Classifying Reported and "Missing" Resonances According to Their P and C Properties
The Hilbert space H^3q of the three quarks with one excited quark is
decomposed into Lorentz group representations. It is shown that the quantum
numbers of the reported and ``missing'' resonances fall apart and populate
distinct representations that differ by their parity or/and charge conjugation
properties. In this way, reported and ``missing'' resonances become
distinguishable. For example, resonances from the full listing reported by the
Particle Data Group are accommodated by Rarita-Schwinger (RS) type
representations (k/2,k/2)*[(1/2,0)+(0,1/2)] with k=1,3, and 5, the highest spin
states being J=3/2^-, 7/2^+, and 11/2^+, respectively. In contrast to this,
most of the ``missing'' resonances fall into the opposite parity RS fields of
highest-spins 5/2^-, 5/2^+, and 9/2^+, respectively. Rarita-Schwinger fields
with physical resonances as lower-spin components can be treated as a whole
without imposing auxiliary conditions on them. Such fields do not suffer the
Velo-Zwanziger problem but propagate causally in the presence of
electromagnetic fields. The pathologies associated with RS fields arise
basically because of the attempt to use them to describe isolated spin-J=k+1/ 2
states, rather than multispin-parity clusters. The positions of the observed RS
clusters and their spacing are well explained trough the interplay between the
rotational-like (k/2)(k/2 +1)-rule and a Balmer-like -(k+1)^{-2}-behavior
Humidity effects on adhesion of nickel-zinc ferrite in elastic contact with magnetic tape and itself
The effects of humidity on the adhesion of Ni-Zn ferrite and magnetic tape in elastic contact with a Ni-Zn ferrite hemispherical pin in moist nitrogen were studied. Adhesion was independent of normal load in dry, humid, and saturated nitrogen. Ferrites adhere to ferrites in a saturated atmosphere primarily from the surface tension effects of a thin film of water adsorbed on the ferrite surfaces. The surface tension of the water film calculated from the adhesion results was 48 times 0.00001 to 56 times 0.00001 N/cm; the accepted value for water is 72.7 x 0.00001 N/cm. The adhesion of ferrite-ferrite contacts increased gradually with increases in relative humidity to 80 percent, but rose rapidly above 80 percent. The adhesion at saturation was 30 times or more greater than that below 80 percent relative humidity. Although the adhesion of magnetic tape - ferrite contacts remained low below 40 percent relative humidity and the effect of humidity was small, the adhesion increased considerably with increasing relative humidity above 40 percent. The changes in adhesion of elastic contacts were reversible on humidifying and dehumidifying
Lorentz Multiplet Structure of Baryon Spectra and Relativistic Description
The pole positions of the various baryon resonances are known to reveal
well-pronounced clustering, so-called Hoehler clusters. For nonstrange baryons
the Hoehler clusters are shown to be identical to Lorentz multiplets of the
type (j,j)*[(1/2,0)+(0,1/2)] with j being a half-integer. For the Lambda
hyperons below 1800 MeV these clusters are shown to be of the type [(1,0)+
(0,1)]*[(1/2,0)+(0,1/2)] while above 1800 MeV they are parity duplicated
(J,0)+(0,J) (Weinberg-Ahluwalia) states. Therefore, for Lambda hyperons the
restoration of chiral symmetry takes place above 1800 MeV. Finally, it is
demonstrated that the description of spin-3/2 particles in terms of a 2nd rank
antisymmetric Lorentz tensor with Dirac spinor components does not contain any
off-shell parameters and avoids the main difficulties of the Rarita-Schwinger
description based upon a 4-vector with Dirac spinor components.Comment: 12 pages, LaTex, submitted to Mod. Phys. Lett.
Solving the Bethe-Salpeter equation for bound states of scalar theories in Minkowski space
We apply the perturbation theory integral representation (PTIR) to solve for
the bound state Bethe-Salpeter (BS) vertex for an arbitrary scattering kernel,
without the need for any Wick rotation. The results derived are applicable to
any scalar field theory (without derivative coupling). It is shown that solving
directly for the BS vertex, rather than the BS amplitude, has several major
advantages, notably its relative simplicity and superior numerical accuracy. In
order to illustrate the generality of the approach we obtain numerical
solutions using this formalism for a number of scattering kernels, including
cases where the Wick rotation is not possible.Comment: 28 pages of LaTeX, uses psfig.sty with 5 figures. Also available via
WWW at
http://www.physics.adelaide.edu.au/theory/papers/ADP-97-10.T248-abs.html or
via anonymous ftp at
ftp://bragg.physics.adelaide.edu.au/pub/theory/ADP-97-10.T248.ps A number of
(crucial) typographical errors in Appendix C corrected. To be published in
Phys. Rev. D, October 199
Does the effective Lagrangian for low-energy QCD scale?
QCD is not an approximately scale invariant theory. Hence a dilaton field is
not expected to provide a good description of the low-energy dynamics
associated with the gluon condensate. Even if such a field is introduced, it
remains almost unchanged in hadronic matter at normal densities. This is
because the large glueball mass together with the size of the phenomenological
gluon condensate ensure that changes to that condensate are very small at such
densities. Any changes in hadronic masses and decay constants in matter
generated by that condensate will be much smaller that those produced directly
by changes in the quark condensate. Hence masses and decay constants are not
expected to display a universal scaling.Comment: 7 pages (RevTeX), MC/TH 94/0
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