3,019 research outputs found
On Mirror Symmetry for Calabi-Yau Fourfolds with Three-Form Cohomology
We study the action of mirror symmetry on two-dimensional N=(2,2) effective
theories obtained by compactifying Type IIA string theory on Calabi-Yau
fourfolds. Our focus is on fourfold geometries with non-trivial three-form
cohomology. The couplings of the massless zero-modes arising by expanding in
these forms depend both on the complex structure deformations and the Kahler
structure deformations of the Calabi-Yau fourfold. We argue that two
holomorphic functions of the deformation moduli capture this information. These
are exchanged under mirror symmetry, which allows us to derive them at the
large complex structure and large volume point. We discuss the application of
the resulting explicit expression to F-theory compactifications and their weak
string coupling limit. In the latter orientifold settings we demonstrate
compatibility with mirror symmetry of Calabi-Yau threefolds at large complex
structure. As a byproduct we find an interesting relation of no-scale like
conditions on Kahler potentials to the existence of chiral and twisted-chiral
descriptions in two dimensions.Comment: 36 page
Quantum statistics with internal symmetry
We formulate a group-theoretical projection technique for the quantum-statistical description of systems with exactly conserved charges corresponding to local non-Abelian gauge symmetries. The formalism is specified for SU(N) internal symmetry and a partition function related to a mixed canonicalâgrand-canonical ensemble is defined. Its perturbation expansion is derived, and we point out potential applications. We also study single-particle Greenâs functions for the calculation of mixed ensemble averages with the help of a generalized Wickâs theorem and find that a connected-graphs expansion is impossible
Automation of the Dipole Subtraction Method in MadGraph/MadEvent
We present the implementation of the dipole subtraction formalism for the
real radiation contributions to any next-to-leading order QCD process in the
MadGraph/MadEvent framework. Both massless and massive dipoles are considered.
Starting from a specific (n+1)-particle process the package provides a Fortran
code for all possible dipoles to all Born processes that constitute the
subtraction term to the (n+1)-particle process. The output files are given in
the usual "MadGraph StandAlone" style using helicity amplitudes.Comment: 14 pages, 4 figure
Integrated dipoles with MadDipole in the MadGraph framework
Heading towards a full automation of next-to-leading order (NLO) QCD
corrections, one important ingredient is the analytical integration over the
one-particle phase space of the unresolved particle that is necessary when
adding the subtraction terms to the virtual corrections. We present the
implementation of these integrated dipoles in the MadGraph framework. The
result is a package that allows an automated calculation for the NLO real
emission parts of an arbitrary process.Comment: 22 pages, 1 figure. Published version: few reference updates and a
couple of minor corrections to the tex
Translationally invariant cumulants in energy cascade models of turbulence
In the context of random multiplicative energy cascade processes, we derive
analytical expressions for translationally invariant one- and two-point
cumulants in logarithmic field amplitudes. Such cumulants make it possible to
distinguish between hitherto equally successful cascade generator models and
hence supplement lowest-order multifractal scaling exponents and multiplier
distributions.Comment: 11 pages, 3 figs, elsart.cls include
Challenge Patient Dispatching in Mass Casualty Incidents
Efficient management of mass casualty incidents is complex, since regular emergency medical services struc-tures have to be switched to a temporary âdisaster modeâ involving additional operational and tactical struc-tures. Most of the relevant decisions have to be taken on-site in a provisional and chaotic environment. Data gathering about affected persons is one side of the coin; the other side is on-site patient dispatching requiring information exchange with the regular emergency call center and destination hospitals. In this paper we extend a previous conference contribution about the research project e-Triage to the aspect of patient data and on-site patient dispatching. Our considerations reflect the situation in Germany, which deserves from our point of view substantial harmonization
Strangeness abundances in pÂŻ-nucleus annihilations
Strange particle abundances in small volumes of hot hadronic gas are determined in the canonical ensemble with exact strangeness and baryon number conservation. Substantial density and baryon number dependence is found. A pÂŻd experiment is examined and applications to pÂŻ-nucleus annihilations are considered
Heat transfer in a beef manure anaerobic digester
In cold climates it was determined that the heat loss from the hot effluent of a beef manure anaerobic digester represented a sizeable portion of the energy production of the digester. This suggested an effluent to influent heat exchanger was necessary. Available heat exchangers were unsuitable;A different concept heat exchanger using a vertical flat plate for the heat transfer surface with the hot and cold flows passing on either side was then considered. The exchanger would be divided into a number of tanks with an overall counterflow arrangement. The extra tanks and the counterflow arrangement would increase the effectiveness. Gravity flow would allow the introduction of gas agitation to keep the solids from settling, prevent plugging, and enhance the heat transfer coefficient. The concept was called a multipass mixed tank exchanger;Design equations and curves for the multipass mixed tank exchanger were developed using the number of transfer units, N(,tu). These equations were suitable for design when the overall thermal conductance, U, was known;A 1.18 m by 2.30 m prototype water to water heat exchanger was constructed and used to verify the design equations. The prototype was to have been used on an anaerobic digester at the ISU Beef Nutrition farm, but the digester was not yet completed at the time of this writing;To determine the convective heat transfer coefficient, h, (from which U can be estimated), and to consider the effects of air agitation, laboratory equipment was constructed. The equipment consisted of a large vertical cylinder with a closed bottom and open top, containing a fixed sample. Heat was applied at a known rate to the outer cylinder. In the center of the sample, a small, water cooled, pipe acted as a heat sink. The h value was determined from the known heat rate and the temperature drop between the sample and the center pipe;The effects of air agitation on h were determined by supplying varying amounts of air at the sample bottom. Sufficient air agitation to completely blend the sample was observed to greatly increase the h value compared to lower air rates. Additional air flow rates had a lesser effect;The experimental results indicated that the h value for a specific manure sample could be predicted by knowing the total solids and the air agitation rate. The h value for effluent could only be partly predicted by knowing the air agitation rate. It was hypothesized that other parameters, such as viscosity and Reynolds number, were necessary. These were not evaluated;The multipass mixed tank exchanger is a possible method to recover lost heat. Further studies are necessary to verify that the concept can be put to practical use
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