1,828 research outputs found
Unusual High-Energy Phenomenology of Lorentz-Invariant Noncommutative Field Theories
It has been suggested that one may construct a Lorentz-invariant
noncommutative field theory by extending the coordinate algebra to additional,
fictitious coordinates that transform nontrivially under the Lorentz group.
Integration over these coordinates in the action produces a four-dimensional
effective theory with Lorentz invariance intact. Previous applications of this
approach, in particular to a specific construction of noncommutative QED, have
been studied only in a low-momentum approximation. Here we discuss
Lorentz-invariant field theories in which the relevant physics can be studied
without requiring an expansion in the inverse scale of noncommutativity.
Qualitatively, we find that tree-level scattering cross sections are
dramatically suppressed as the center-of-mass energy exceeds the scale of
noncommutativity, that cross sections that are isotropic in the commutative
limit can develop a pronounced angular dependence, and that nonrelativistic
potentials (for example, the Coloumb potential) become nonsingular at the
origin. We consider a number of processes in noncommutative QED that may be
studied at a future linear collider. We also give an example of scattering via
a four-fermion operator in which the noncommutative modifications of the
interaction can unitarize the tree-level amplitude, without requiring any other
new physics in the ultraviolet.Comment: 24 pages LaTeX, 4 eps figures (v2: reference added, v3: minor
clarifications
Pion Form Factors in Holographic QCD
Using a holographic dual model of QCD, we compute the pion electromagnetic
form factor F_pi(Q^2) in the spacelike momentum transfer region, as well as
pion couplings to vector mesons g_rho^(n) pi pi. Spontaneous and explicit
chiral symmetry breaking are intrinsic features of this particular holographic
model. We consider variants with both ``hard-wall'' and ``soft-wall'' infrared
cutoffs, and find that the F_pi(Q^2) data tend to lie closer to the hard-wall
model predictions, although both are too shallow for large Q^2. By allowing the
parameters of the soft-wall model (originally fixed by observables such as
m_rho) to vary, one finds fits that tend to agree better with F_pi(Q^2). We
also compute the pion charge radius for a variety of parameter
choices, and use the values of f^(n)_rho, g_{rho^(n) pi pi} and m^(n)_rho to
observe the saturation of F_pi(0) by rho poles.Comment: 17 pages, 2 figures, revised fits using consistent normalization of
f_pi. References update
AdS/QCD and Light Front Holography: A New Approximation to QCD
The combination of Anti-de Sitter space (AdS) methods with light-front
holography leads to a semi-classical first approximation to the spectrum and
wavefunctions of meson and baryon light-quark bound states. Starting from the
bound-state Hamiltonian equation of motion in QCD, we derive relativistic
light-front wave equations in terms of an invariant impact variable zeta which
measures the separation of the quark and gluonic constituents within the hadron
at equal light-front time. These equations of motion in physical space-time are
equivalent to the equations of motion which describe the propagation of spin-J
modes in anti--de Sitter (AdS) space. Its eigenvalues give the hadronic
spectrum, and its eigenmodes represent the probability distributions of the
hadronic constituents at a given scale. Applications to the light meson and
baryon spectra are presented. The predicted meson spectrum has a string-theory
Regge form ; i.e., the square of the
eigenmass is linear in both L and n, where n counts the number of nodes of the
wavefunction in the radial variable zeta. The space-like pion and nucleon form
factors are also well reproduced. One thus obtains a remarkable connection
between the description of hadronic modes in AdS space and the Hamiltonian
formulation of QCD in physical space-time quantized on the light-front at fixed
light-front time. The model can be systematically improved by using its
complete orthonormal solutions to diagonalize the full QCD light-front
Hamiltonian or by applying the Lippmann-Schwinger method in order to
systematically include the QCD interaction terms.Comment: Invited talk, presented by SJB at the Fifth International Conference
On Quarks and Nuclear Physics (QNP09), 21-26 Sep 2009, Beijing, China. Figure
update
Novel technique for thermal lens measurement in commonly used optical components
The absorption of light in transmissive optics cause a thermally
induced effect known as thermal lensing. This effect provokes an often
undesired change of a laser beam transmitted by the optic. In this paper we
present a measurement method that allows us to determine thermal lensing
in commonly used optical components. The beam influenced by the thermal
lens is expanded into the eigenmodes of an optical cavity, and its modal
content is analyzed in the eigenbasis of the cavity. The measured quantity
depends neither on beam parameters nor on the position of the optical
component under investigation. This method allows, to our knowledge, for
the first time the direct measurement of the mode conversion coefficient je2j
of the thermal lens
The Clusters AgeS Experiment (CASE). I. V209 omega Cen - An Eclipsing Post-Common Envelope Binary in the Globular Cluster omega Cen
We use photometric and spectroscopic observations of the detached eclipsing
binary V209 omega Cen to derive the masses, radii, and luminosities of the
component stars. The system exhibits total eclipses and, based on the measured
systemic velocity and the derived distance, is a member of the globular cluster
omega Cen. We obtain 0.945 +/- 0.043 Msun, 0.983 +/- 0.015 Rsun and 6.68 +/-
0.88 Lsun for the cooler, but larger and more luminous primary component. The
secondary component has 0.144 +/- 0.008 Msun, 0.425 +/- 0.008 Rsun and 2.26 +/-
0.28 Lsun. The effective temperatures are estimated at 9370 K for the primary
and at 10866 K for the secondary. On the color-magnitude diagram of the
cluster, the primary component occupies a position between the tip of the blue
straggler region and the extended horizontal branch while the secondary
component is located close to the red border of the area occupied by hot
subdwarfs. However, its radius is too large and its effective temperature is
too low for it to be an sdB star. We propose a scenario leading to the
formation of a system with such unusual properties with the primary component
``re-born'' from a former white dwarf which accreted a new envelope through
mass transfer from its companion. The secondary star has lost most of its
envelope while starting its ascent onto the sub-giant branch. It failed to
ignite helium in its core and is currently powered by a hydrogen burning shell.Comment: 24 pages, 9 figures, AJ, in pres
Rancang Bangun Sistem Informasi Penjadwalan Produksi Berdasarkan Jadwal Pesanan Barang pada PT. Bioli Lestari
Bioli Lestari is one of the company that run manufacturing industry. This company have problems at controlling their production schedule to fulfill customer product orders. The problem arise because their schedule based on raw material which available at the time, not based on costumer order. Production schedule problem cause company can't give information about product finish due to the costumer. Based on problem explained before, a system that can handle customer orders and can make production schedule based on customers order being needed. In this case system use Shortest Processing Time (SPT) as a method to create production schedule, after that system will create production schedule based on customer orders which can help company to answer customers question about product orders finish due and can help company run production process based on customers order
The Clusters AgeS Experiment (CASE). II. The Eclipsing Blue Straggler OGLEGC-228 in the Globular Cluster 47 Tuc
We use photometric and spectroscopic observations of the eclipsing binary
OGLEGC-228 (V228) to derive the masses, radii, and luminosities of the
component stars. Based on measured systemic velocity, proper motion and
distance, the system is a blue straggler member of the globular cluster 47 Tuc.
Our analysis shows that V228 is a semi-detached Algol. We obtain M=1.512 +/-
0.022 Msun, R=1.357 +/- 0.019 Rsun, L=7.02 +/- 0.050 Lsun for the hotter and
more luminous primary component and M=0.200 +/- 0.007 Msun, R=1.238 +/- 0.013
Rsun, L=1.57 +/- 0.09 Lsun for the Roche lobe filling secondary.Comment: 19 pages, 5 figures, AJ, in pres
Surgical Treatment of Neuropathic Chronic Postherniorrhaphy Inguinal Pain:A Systematic Review and Meta-Analysis
Background/Objectives: Neuropathic chronic postherniorrhaphy inguinal pain (CPIP) is a serious adverse outcome following inguinal hernia repair surgery. The optimal surgical treatment for neuropathic CPIP remains controversial in the current literature. This systematic review aims to evaluate the effectiveness of various surgical techniques utilized to manage neuropathic CPIP. Methods: The electronic databases Medline, Embase, Web of Science, Cochrane Central, and Google Scholar were searched. Inclusion criteria were defined to select studies reporting on the efficacy of surgical interventions in patients with neuropathic CPIP. The primary outcome was postoperative pain relief, as determined by postoperative numerical or nonnumerical pain scores. Results: Ten studies met the inclusion criteria. Three surgical techniques were identified: selective neurectomy, triple neurectomy, and targeted muscle reinnervation. Proportions of good postoperative results of the surgical techniques ranged between 46 and 88 percent. Overall, the surgical treatment of neuropathic CPIP achieved a good postoperative result in 68 percent (95% CI, 49 to 82%) of neuropathic CPIP patients (n = 244), with targeted muscle reinnervation yielding the highest proportion of good postoperative results. Conclusions: The surgical treatment of neuropathic CPIP is generally considered safe and has demonstrated effective pain relief across various surgical techniques. Targeted muscle reinnervation exhibits considerable potential for surpassing current success rates in inguinal hernia repair surgery.</p
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