3,285 research outputs found
Quantum power correction to the Newton law
We have found the graviton contribution to the one-loop quantum correction to
the Newton law. This correction results in interaction decreasing with distance
as 1/r^3 and is dominated numerically by the graviton contribution. The
previous calculations of this contribution to the discussed effect are
demonstrated to be incorrect.Comment: 10 pages, 5 figures; numerical error corrected, few references adde
Methods of selecting and using therapeutic and prophylactic probiotic cultures to reduce bacterial pathogen loads
Methods are provided for selecting a bacterium capable of reducing pathogenic bacterial colonization of the intestinal tract in a subject comprising selecting the bacterium capable of migrating at least 0.75 cm from the point of inoculation on motility agar after incubation for 24 hours at 37° C. It is also capable of migrating from the point of inoculation to a diameter of at least 1.5 cm based on the farthest colonies from the point of inoculation on motility agar after incubation for 24 hours at 37° C. Bacteria selected using the method and compositions comprising these bacteria are also provided
The anthropic principle and the mass scale of the Standard Model
In theories in which different regions of the universe can have different
values of the the physical parameters, we would naturally find ourselves in a
region which has parameters favorable for life. We explore the range of
anthropically allowed values of the mass parameter in the Higgs potential,
. For , the requirement that complex elements be formed
suggests that the Higgs vacuum expectation value must have a magnitude less
than 5 times its observed value. For , baryon stability requires that
, the Planck Mass. Smaller values of may or may not be
allowed depending on issues of element synthesis and stellar evolution. We
conclude that the observed value of is reasonably typical of the
anthropically allowed range, and that anthropic arguments provide a plausible
explanation for the closeness of the QCD scale and the weak scale.Comment: 28 pages, LaTeX. No changes from version originally submitted to
archive, except that problem with figure file has been correcte
Widespread occurrence of Mycobacterium tuberculosis DNA from 18th-19th century Hungarians
A large number (265) of burials from 1731-1838 were discovered in sealed crypts of the Dominican Church, Vac, Hungary in 1994. Many bodies were naturally mummified, so that both soft tissues and bones were available. Contemporary archives enabled the determination of age at death, and the identification of family groups. In some cases, symptoms before death were described and, occasionally, occupation. Initial radiological examination of a small number of individuals had indicated calcified lung lesions and demonstrable acid-fast bacteria suggestive of tuberculosis infection. Tuberculosis was endemic in 18th-19th century Europe, so human remains should contain detectable Mycobacterium tuberculosis complex (MTB) DNA, enabling comparisons with modern isolates. Therefore, a comprehensive examination of 168 individuals for the presence of MTB DNA was undertaken. Specific DNA amplification methods for MTB showed that 55% of individuals were positive and that the incidence varied according to age at death and sampling site in the body. Radiographs were obtained from 27 individuals and revealed an association between gross pathology and the presence of MTB DNA. There was an inverse relationship between PCR positivity and MTB target sequence size. In some cases, the preservation of MTB DNA was excellent, and several target gene sequences could be detected from the same sample. This information, combined with MTB DNA sequencing data and molecular typing techniques, will enable us to study the past epidemiology of TB infection, and extends the timeframe for studying changes in molecular fingerprints. Am J Phys Anthropol 120:144-152, 2003. (C) 2003 Wiley-Liss, Inc
The Mixed Vector Current Correlator <0|T(V^3_\mu V^8_\nu )|0> To Two Loops in Chiral Perturbation Theory
The isospin-breaking correlator of the product of flavor octet vector
currents, and , is computed to
next-to-next- to-leading (two-loop) order in Chiral Perturbation Theory. Large
corrections to both the magnitude and -dependence of the one-loop result
are found, and the reasons for the slow convergence of the chiral series for
the correlator given. The two-loop expression involves a single
counterterm, present also in the two-loop expressions for
and , which counterterm
contributes a constant to the scalar correlator . The
feasibility of extracting the value of this counterterm from other sources is
discussed. Analysis of the slope of the correlator with respect to using
QCD sum rules is shown to suggest that, even to two-loop order, the chiral
series for the correlator may not yet be well-converged.Comment: 32 pages, uses REVTEX and epsfig.sty with 7 uuencoded figures. Entire
manuscript available as a ps file at
http://www.physics.adelaide.edu.au/theory/home.html Also available via
anonymous ftp at ftp://adelphi.adelaide.edu.au/pub/theory/ADP-95-27.T181.p
Absorptive part of meson--baryon scattering amplitude and baryon polarization in chiral perturbation theory
We compute the spin asymmetry and polarization of the final-state baryon in
its rest frame in two-body meson--baryon low-energy scattering with unpolarized
initial state, to lowest non-trivial order in BChPT. The required absorptive
amplitudes are obtained analytically at one-loop level. We discuss the
polarization results numerically for several meson--baryon processes. Even at
low energies above threshold, where BChPT can reasonably be expected to be
applicable, sizable values of polarization are found for some processes
Photon-Photon Scattering, Pion Polarizability and Chiral Symmetry
Recent attempts to detect the pion polarizability via analysis of
measurements are examined. The connection
between calculations based on dispersion relations and on chiral perturbation
theory is established by matching the low energy chiral amplitude with that
given by a full dispersive treatment. Using the values for the polarizability
required by chiral symmetry, predicted and experimental cross sections are
shown to be in agreement.Comment: 21 pages(+10 figures available on request), LATEX, UMHEP-38
Fermion masses in noncommutative geometry
Recent indications of neutrino oscillations raise the question of the
possibility of incorporating massive neutrinos in the formulation of the
Standard Model (SM) within noncommutative geometry (NCG). We find that the NCG
requirement of Poincare duality constrains the numbers of massless quarks and
neutrinos to be unequal unless new fermions are introduced. Possible scenarios
in which this constraint is satisfied are discussed.Comment: 4 pages, REVTeX; typos are corrected in (19), "Possible Solutions"
and "Conclusion" are modified; additional calculational details are included;
references are update
On the Ultraviolet Behaviour of Newton's constant
We clarify a point concerning the ultraviolet behaviour of the Quantum Field
Theory of gravity, under the assumption of the existence of an ultraviolet
Fixed Point. We explain why Newton's constant should to scale like the inverse
of the square of the cutoff, even though it is technically inessential. As a
consequence of this behaviour, the existence of an UV Fixed Point would seem to
imply that gravity has a built-in UV cutoff when described in Planck units, but
not necessarily in other units.Comment: 8 pages; CQG class; minor changes and rearrangement
Final state rescattering as a contribution to
We provide a new estimate of the long-distance component to the radiative
transition . Our mechanism involves the soft-scattering of
on-shell hadronic products of nonleptonic decay, as in the chain . We employ a phenomenological fit to scattering data
to estimate the effect. The specific intermediate states considered here modify
the decay rate at roughly the level, although
the underlying effect has the potential to be larger. Contrary to other
mechanisms of long distance physics which have been discussed in the
literature, this yields a non-negligible modification of the channel and hence will provide an uncertainty in the extraction of
. This mechanism also affects the isospin relation between the rates
for and and may generate CP
asymmetries at experimentally observable levels.Comment: 15 pages, RevTex, 3 figure
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