545 research outputs found
Effects of Relativistic Dynamics in near Threshold
The cross-section for threshold production in proton-proton
collisions is evaluated in the framework of the covariant spectator
description. The negative energy intermediate states are included
non-perturbatively and seen to yield a considerably smaller contribution, when
compared to perturbative treatments. A family of OBE-models with different
off-shell scalar coupling is considered.Comment: 10 pages, 3 figures, 1 tabl
Qualitätssicherung interdisziplinärer Polytraumaversorgung: Möglichkeiten und Grenzen retrospektiver Standarderfassung
Zusammenfassung: Hintergrund: Inwieweit kann die Auswertung standardmäßig erhobener Patienten- und Krankenhausdaten einen Behandlungsvergleich mit anderen Erhebungen gestatten? Material und Methoden: Es wurde eine retrospektive Analyse epidemiologischer und klinisch-technischer Parameter aller Mehrfachverletzten [Injury Severity Score (ISS)>15] einer Zentrumsklinik (n=172; Zeitraum: 01.01.1997-31.12.1999) bezüglich der Ablauforganisation und des Outcome (p74Jahre, Hypotension, initial verminderte Hämoglobin- und Quick-Werte, verminderte Glasgow Coma Scale (GCS) sowie Anzahl erhaltener Blutkonzentrate. Eine Gegenüberstellung der erhobenen Daten mit der zeitgleichen prospektiven Multizenterstudie der Deutschen Gesellschaft für Unfallchirurgie (DGU) bestätigte die Ergebnisse bezüglich des Ablaufs und des Outcome. Schlussfolgerung: Die interdisziplinäre retrospektive Datenauswertung ist unter Fokussierung auf prognoserelevante und routinemäßig erhobene Parameter eine praktikable sowie aussagefähige Alternative zu prospektiven Erfassungen und ermöglicht eine erste qualitative Standortbestimmun
Deformed Superspace, N=1/2 Supersymmetry and (Non)Renormalization Theorems
We consider a deformed superspace in which the coordinates \theta do not
anticommute, but satisfy a Clifford algebra. We present results on the
properties of N=1/2 supersymmetric theories of chiral superfields in deformed
superspace, taking the Wess-Zumino model as the prototype. We prove new
(non)renormalization theorems: the F-term is radiatively corrected and becomes
indistinguishable from the D-term, while the Fbar-term is not renormalized.
Supersymmetric vacua are critical points of the antiholomorphic superpotential.
The vacuum energy is zero to all orders in perturbation theory. We illustrate
these results with several examples.Comment: 21 pages, 5 figures and one table; V2: references adde
Finite gravitational action for higher derivative and stringy gravities
We generalize the local surface counterterm prescription suggested in
Einstein gravity for higher derivative (HD) and Weyl gravities. Explicitly, the
surface counterterm is found for three- and five-dimensional HD gravities. As a
result, the gravitational action for asymptotically AdS spaces is finite and
gravitational energy-momentum tensor is well-defined. The holographic trace
anomaly for d2 and d4 boundary (gauge) QFT dual to above HD gravity is
calculated from gravitational energy-momentum tensor. The calculation of AdS
black hole mass in HD gravity is presented within above prescrition. The
comparison with the standard prescription (using reference spacetime) is done.Comment: LaTeX file, 21 page
Efimov Trimers near the Zero-crossing of a Feshbach Resonance
Near a Feshbach resonance, the two-body scattering length can assume any
value. When it approaches zero, the next-order term given by the effective
range is known to diverge. We consider the question of whether this divergence
(and the vanishing of the scattering length) is accompanied by an anomalous
solution of the three-boson Schr\"odinger equation similar to the one found at
infinite scattering length by Efimov. Within a simple zero-range model, we find
no such solutions, and conclude that higher-order terms do not support Efimov
physics.Comment: 8 pages, no figures, final versio
There is no "Theory of Everything" inside E8
We analyze certain subgroups of real and complex forms of the Lie group E8,
and deduce that any "Theory of Everything" obtained by embedding the gauge
groups of gravity and the Standard Model into a real or complex form of E8
lacks certain representation-theoretic properties required by physical reality.
The arguments themselves amount to representation theory of Lie algebras in the
spirit of Dynkin's classic papers and are written for mathematicians.Comment: Final version, to appear in Communications in Mathematical Physics.
The main difference, from the previous version, is the creation of a new
section, containing a response to Lisi's objections to our wor
U(N) Instantons on N=1/2 superspace -- exact solution & geometry of moduli space
We construct the exact solution of one (anti)instanton in N=1/2 super
Yang-Mills theory defined on non(anti)commutative superspace. We first identify
N = 1/2 superconformal invariance as maximal spacetime symmetry. For gauge
group U(2), SU(2) part of the solution is given by the standard
(anti)instanton, but U(1) field strength also turns out nonzero. The solution
is SO(4) rotationally symmetric. For gauge group U(N), in contrast to the U(2)
case, we show that the entire U(N) part of the solution is deformed by
non(anti)commutativity and fermion zero-modes. The solution is no longer
rotationally symmetric; it is polarized into an axially symmetric configuration
because of the underlying non(anti)commutativity. We compute the `information
metric' of one (anti) instanton. We find that moduli space geometry is deformed
from hyperbolic space (Euclidean anti-de Sitter space) in a way anticipated
from reduced spacetime symmetry. Remarkably, the volume measure of the moduli
space turns out to be independent of the non(anti)commutativity. Implications
to D-branes in Ramond- Ramond flux background and Maldacena's gauge-gravity
correspondence are discussed.Comment: 39 pages, 3 figures, JHEP style; v2. typos corrected + a paragraph
adde
Vector meson production and nucleon resonance analysis in a coupled-channel approach for energies m_N < sqrt(s) < 2 GeV I: pion-induced results and hadronic parameters
We present a nucleon resonance analysis by simultaneously considering all
pion- and photon-induced experimental data on the final states gamma N, pi N, 2
pi N, eta N, K Lambda, K Sigma, and omega N for energies from the nucleon mass
up to sqrt(s) = 2 GeV. In this analysis we find strong evidence for the
resonances P_{31}(1750), P_{13}(1900), P_{33}(1920), and D_{13}(1950). The
omega N production mechanism is dominated by large P_{11}(1710) and
P_{13}(1900) contributions. In this first part, we present the results of the
pion-induced reactions and the extracted resonance and background properties
with emphasis on the difference between global and purely hadronic fits.Comment: 54 pages, 26 figures, discussion extended, typos corrected,
references updated, to appear in Phys. Rev.
- …