823 research outputs found
On gauge unification in Type I/I' models
We discuss whether the (MSSM) unification of gauge couplings can be
accommodated in string theories with a low (TeV) string scale. This requires
either power law running of the couplings or logarithmic running extremely far
above the string scale. In both cases it is difficult to arrange for the
multiplet structure to give the MSSM result. For the case of power law running
there is also enhanced sensitivity to the spectrum at the unification scale.
For the case of logarithmic running there is a fine tuning problem associated
with the light closed string Kaluza Klein spectrum which requires gauge
mediated supersymmetry breaking on the ``visible'' brane with a dangerously low
scale of supersymmetry breaking. Evading these problems in low string scale
models requires a departure from the MSSM structure, which would imply that the
success of gauge unification in the MSSM is just an accident.Comment: 10 pages, LaTeX, 2 figures; minor change
Dense Quarks, and the Fermion Sign Problem, in a SU(N) Matrix Model
We study the effect of dense quarks in a SU(N) matrix model of deconfinement.
For three or more colors, the quark contribution to the loop potential is
complex. After adding the charge conjugate loop, the measure of the matrix
integral is real, but not positive definite. In a matrix model, quarks act like
a background Z(N) field; at nonzero density, the background field also has an
imaginary part, proportional to the imaginary part of the loop. Consequently,
while the expectation values of the loop and its complex conjugate are both
real, they are not equal. These results suggest a possible approach to the
fermion sign problem in lattice QCD.Comment: 9 pages, 3 figure
Spatiotemporal discrete multicolor solitons
We have found various families of two-dimensional spatiotemporal solitons in
quadratically nonlinear waveguide arrays. The families of unstaggered odd, even
and twisted stationary solutions are thoroughly characterized and their
stability against perturbations is investigated. We show that the twisted and
even solutions display instability, while most of the odd solitons show
remarkable stability upon evolution.Comment: 18 pages,7 figures. To appear in Physical Review
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Identifying jumps in financial assets: A comparison between nonparametric jump tests
We perform a comprehensive Monte Carlo comparison between nine alternative procedures available in the literature to detect jumps in financial assets using high-frequency data. We evaluate size and power properties of the procedures under alternative sampling frequencies, persistence in volatility, jump size and intensity, and degree of contamination with microstructure noise. The overall best performance is shown by the Andersen, Bollerslev, and Dobrev (2007) and Lee and Mykland (2008) intraday procedures (ABD-LM), provided the price process is not very volatile. We propose two extensions to the existing battery of tests. The first regards the finite sample improvements based on simulated critical values for the ABD-LM procedure. The second regards a procedure that combines frequencies and tests able to reduce the number of spurious jumps. Finally, we report an empirical analysis using real high frequency data on five stocks listed in the New York Stock Exchange
BRAHMS Overview
A brief review of BRAHMS measurements of bulk particle production in RHIC
Au+Au collisions at is presented, together with some
discussion of baryon number transport. Intermediate measurements in
different collision systems (Au+Au, d+Au and p+p) are also discussed in the
context of jet quenching and saturation of the gluon density in Au ions at RHIC
energies. This report also includes preliminary results for identified
particles at forward rapidities in d+Au and Au+Au collisions.Comment: 8 pages 6 figures, Invited plenary talk at 5th International
Conference on Physics and Astrophysics of Quark Gluon Plasma (ICPAQGP 2005),
Salt Lake City, Kolkata, India, 8-12 Feb 200
Pomeron loop and running coupling effects in high energy QCD evolution
Within the framework of a (1+1)-dimensional model which mimics evolution and
scattering in QCD at high energy, we study the influence of the running of the
coupling on the high-energy dynamics with Pomeron loops. We find that the
particle number fluctuations are strongly suppressed by the running of the
coupling, by at least one order of magnitude as compared to the case of a fixed
coupling, for all the rapidities that we have investigated, up to Y=200. This
reflects the slowing down of the evolution by running coupling effects, in
particular, the large rapidity evolution which is required for the formation of
the saturation front via diffusion. We conclude that, for all energies of
interest, processes like deep inelastic scattering or forward particle
production can be reliably studied within the framework of a mean-field
approximation (like the Balitsky-Kovchegov equation) which includes running
coupling effects.Comment: 23 pages, 8 figure
THE EFFECT OF ORGANIC FERTILIZATION ON FRUIT PRODUCTION AND QUALITY OF TOMATOES GROWN IN THE SOLAR
The purpose of this study was to observe the effect of organic fertilization on the production and quality of tomato fruits grown in early culture in the solar. The influence of this fertilizer was followed in 2017 in a tomato crop in southwestern Romania (AlmÄj-Dolj). The Reyana hybrid was studied which was foliarly fertilized with the organic product Folicist in the doses of 0.5 l/ha, 1.0 l/ha and 1.5 l/ha. The parameters traced were: production, humidity, soluble dry substance, titratable acidity, vitamin C content, total polyphenols and carotenes as well as fruit pH. The highest yield of 12.76 t/ha was obtained at a dose of 1.0 l/ha and also at the same dose were recorded the best quality parameters of the fruit, such as: S.D.S. was 4.7 oBx, humidity of 90.3%, titre acidity of 1.33 mg/NaOH/100g f.m., vitamin C of 24.3 mg/100g f.m., total polyphenols 66.4 mg/100g f.m., total carotenes 51.3 mg/100g f.m. and pH 4.49.ĂÂ These results show that an adequate fertilization of plants with nutrients substances is crucial to achieving high yields and good-tasting fruits.Ă
The K/pi ratio from condensed Polyakov loops
We perform a field-theoretical computation of hadron production in large
systems at the QCD confinement phase transition associated with restoration of
the Z(3) global symmetry. This occurs from the decay of a condensate for the
Polyakov loop. From the effective potential for the Polyakov loop, its mass
just below the confinement temperature T_c is in between the vacuum masses of
the pion and that of the kaon. Therefore, due to phase-space restrictions the
number of produced kaons is roughly an order of magnitude smaller than that of
produced pions, in agreement with recent results from collisions of gold ions
at the BNL-RHIC. From its mass, we estimate that the Polyakov loop condensate
is characterized by a (spatial) correlation scale of 1/m_\ell ~ 1/2 fm. For
systems of deconfined matter of about that size, the free energy may not be
dominated by a condensate for the Polyakov loop, and so the process of
hadronization may be qualitatively different as compared to large systems. In
that vein, experimental data on hadron abundance ratios, for example K/pi, in
high-multiplicity pp events at high energies should be very interesting.Comment: 7 pages, 4 figures; discussion of the two-point function of Polyakov
Loops in small versus large systems adde
Polyakov Loops versus Hadronic States
The order parameter for the pure Yang-Mills phase transition is the Polyakov
loop which encodes the symmetries of the Z_N center of the SU(N) gauge group.
On the other side the physical degrees of freedom of any asymptotically free
gauge theory are hadronic states. Using the Yang-Mills trace anomaly and the
exact Z_N symmetry we construct a model able to communicate to the hadrons the
information carried by the order parameter.Comment: RevTex4 2-col., 6 pages, 2 figures. Typos fixed and added a paragraph
in the conclusion
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