8,579 research outputs found
Some consequences of GUP induced ultraviolet wavevector cutoff in one-dimensional Quantum Mechanics
A projection method is proposed to treat the one-dimensional Schrodinger
equation for a single particle when the Generalized Uncertainty Principle (GUP)
generates an ultraviolet (UV) wavevector cutoff. The existence of a unique
coordinate representation called the naive one is derived from the
one-parameter family of discrete coordinate representations. In this
bandlimited Quantum Mechanics a continuous potential is reconstructed from
discrete sampled values observed by means of a particle in maximally localized
states. It is shown that bandlimitation modifies the speed of the center and
the spreading time of a Gaussian wavepacket moving in free space. Indication is
found that GUP accompanied by bandlimitation may cause departures of the
low-lying energy levels of a particle in a box from those in ordinary Quantum
Mechanics much less suppressed than commonly thought when GUP without
bandlimitation is in work.Comment: 20 pages, 2 figure
Phase structure of the ghost model with higher-order gradient term
The phase structure and the infrared behaviour of the Euclidean 3-dimensional
symmetric ghost scalar field model with higher-order derivative term has
been investigated in Wegner and Houghton's renormalization group framework. The
symmetric phase in which no ghost condensation occurs and the phase with
restored symmetry but with a transient presence of a ghost condensate have been
identified. Finiteness of the correlation length at the phase boundary hints to
a phase transition of first order. The results are compared with those for the
ordinary symmetric scalar field model.Comment: 15 pages, 13 figure
Ordering variable for parton showers
The parton splittings in a parton shower are ordered according to an ordering
variable, for example the transverse momentum of the daughter partons relative
to the direction of the mother, the virtuality of the splitting, or the angle
between the daughter partons. We analyze the choice of the ordering variable
and conclude that one particular choice has the advantage of factoring softer
splittings from harder splittings graph by graph in a physical gauge.Comment: 28 pages, 5 figure
Multi-jet cross sections in deep inelastic scattering at next-to-leading order
We present the perturbative prediction for three-jet production cross section
in DIS at the NLO accuracy. We study the dependence on the renormalization and
factorization scales of exclusive three-jet cross section. The perturbative
prediction for the three-jet differential distribution as a function of the
momentum transfer is compared to the corresponding data obtained by the H1
collaboration at HERA.Comment: 5 pages, 3 figure
Three-jet cross sections in hadron-hadron collisions at next-to-leading order
We present a new QCD event generator for hadron collider which can calculate
one-, two- and three-jet cross sections at next-to-leading order accuracy. In
this letter we study the transverse energy spectrum of three-jet hadronic
events using the kT algorithm. We show that the next-to-leading order
correction significantly reduces the renormalization and factorization scale
dependence of the three-jet cross section.Comment: 4 pages, 4 figures, REVTEX
QCD corrections to e+ e- --> 4 jets
We report on the next-to-leading order QCD calculation for e+ e- --> 4 jets.
We explain some modern techniques which have been used to calculate the
one-loop amplitudes efficiently. We further report on the general purpose
numerical program ``Mercutio'', which can be used to calculate any infrared
safe four-jet quantity in electron-positron annihilation at next-to-leading
order.Comment: 4 pages, talk given at the UK Phenomenology Workshop on Collider
Physics, Durham, 19-24 September 199
CH observations toward the Orion Bar
CH is one of the first radicals to be detected in the interstellar
medium. Its higher rotational transitions have recently become available with
the Herschel Space Observatory. We aim to constrain the physical parameters of
the CH emitting gas toward the Orion Bar. We analyse the CH line
intensities measured toward the Orion Bar CO Peak and Herschel/HIFI maps of
CH, CH, and HCO, and a NANTEN map of [CI]. We interpret the observed
CH emission using radiative transfer and PDR models. Five rotational
transitions of CH have been detected in the HIFI frequency range toward the
CO peak. A single component rotational diagram gives a rotation temperature
of ~64 K and a beam-averaged CH column density of 410
cm. The measured transitions cannot be explained by any single parameter
model. According to a non-LTE model, most of the CH column density produces
the lower- CH transitions and traces a warm ( ~ 100-150 K)
and dense ((H)~10-10 cm) gas. A small fraction of the
CH column density is required to reproduce the intensity of the highest-
transitions (=9-8 and N=10-9) originating from a high density
((H)~510 cm) hot ( ~ 400 K) gas. The
total beam-averaged CH column density in the model is 10 cm.
Both the non-LTE radiative transfer model and a simple PDR model representing
the Orion Bar with a plane-parallel slab of gas and dust suggest, that CH
cannot be described by a single pressure component, unlike the reactive ion
CH, which was previously analysed toward the Orion Bar CO peak. The
physical parameters traced by the higher rotational transitions
(=6-5,...,10-9) of CH may be consistent with the edges of dense clumps
exposed to UV radiation near the ionization front of the Orion Bar.Comment: Proposed for acceptance in A&A, abstract abridge
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