Search results for "PLASMA"
showing 10 items of 4043 documents
Cascade simulation of ultrarelativistic collisions
1988
The dynamics of hot matter produced in ultrarelativistic heavy-ion collisions is studied with a cascade simulation. We model the putative quark-gluon plasma with independent globs of high-density matter. The hadronic phase is treated by explicit tracking of pion coordinates. We find that the pions make 0--2 collisions with globs and 1--3 collisions with other pions, under conditions expected for heavy ions at collider energies. The entropy increases by about 20% during the phase transition. The transverse momentum in the final state is almost entirely due to the momentum with which pions are emitted from the globs, except at extremely high densities where the hydrodynamic expansion of the p…
Calculation of theO(? s 2 ) parity-violating structure functions in $$e^ + e^ - \to q\bar qg$$
1986
We calculate the two nonvanishingO(αs2) parity-violating structure functions that contribute to\(e^ + e^ - \xrightarrow{{\gamma ,Z}}q\bar qg\). We discuss how these can be measured. We work with massless quarks and gluons and use dimensional regularization to regularize ultra-violet and infrared singularities. We carefully discuss how to deal withγ5 in the dimensional regularization scheme when infrared singularities are present.
Search for exotic spin-dependent interactions with a spin-based amplifier
2021
Description
nPDF constraints from the large hadron electron collider
2016
An updated analysis regarding the expected nuclear PDF constraints from the future Large Hadron Electron Collider (LHeC) experiment is presented. The new study is based on a more flexible small-$x$ parametrization which provides less biased uncertainty estimates in the region where there are currently no data constraints. The effect of the LHeC is quantified by directly including a sample of pseudodata according to the expected precision of this planned experiment. As a result, a significant reduction of the small-$x$ uncertainties in sea quarks and gluons is observed.
Synchronized rotation in swarms of magnetotactic bacteria.
2017
Self-organizing behavior has been widely reported in both natural and artificial systems, typically distinguishing between temporal organization (synchronization) and spatial organization (swarming). Swarming has been experimentally observed in systems of magnetotactic bacteria under the action of external magnetic fields. Here we present a model of ensembles of magnetotactic bacteria in which hydrodynamic interactions lead to temporal synchronization in addition to the swarming. After a period of stabilization during which the bacteria form a quasiregular hexagonal lattice structure, the entire swarm begins to rotate in a direction opposite to the direction of the rotation of the magnetic …
Coronal fuzziness modelled with pulse-heated multistranded loop systems
2010
Coronal active regions are observed to get fuzzier and fuzzier (i.e. more and more confused and uniform) in harder and harder energy bands or lines. We explain this evidence as due to the fine multi-temperature structure of coronal loops. To this end, we model bundles of loops made of thin strands, each heated by short and intense heat pulses. For simplicity, we assume that the heat pulses are all equal and triggered only once in each strand at a random time. The pulse intensity and cadence are selected so as to have steady active region loops ($\sim 3$ MK), on the average. We compute the evolution of the confined heated plasma with a hydrodynamic loop model. We then compute the emission al…
Dissipation-induced coherent structures in Bose-Einstein condensates.
2008
We discuss how to engineer the phase and amplitude of a complex order parameter using localized dissipative perturbations. Our results are applied to generate and control various types of atomic nonlinear matter waves (solitons) by means of localized dissipative defects.
Synchronizing Quantum Harmonic Oscillators through Two-Level Systems
2017
Two oscillators coupled to a two-level system which in turn is coupled to an infinite number of oscillators (reservoir) are considered, bringing to light the occurrence of synchronization. A detailed analysis clarifies the physical mechanism that forces the system to oscillate at a single frequency with a predictable and tunable phase difference. Finally, the scheme is generalized to the case of $N$ oscillators and $M(<N)$ two-level systems.
Non-equilibrium Thermodynamical Description of Superfluid Transition in Liquid Helium
2017
In previous papers a phase field model for λ-transition in 4He was proposed, which is able to describe the influence of the heat flux on the temperature transition. The model presented here generalizes previous results taking into account of a homogeneous presence of quantized vortices below the λ-transition. As parameter that controls the transition, a dimensionless field f linked to the modulus of the condensate wave function is used. In addition to the field f , the resulting model chooses the following field variables: Density, velocity, temperature and heat flux. Nonlocal terms to describe inhomogeneities in the field variables and dissipative effects of mechanical and thermal origin…
Finite-size scaling for a first-order transition where a continuous symmetry is broken: The spin-flop transition in the three-dimensional XXZ Heisenb…
2019
Finite-size scaling for a first-order phase transition where a continuous symmetry is broken is developed using an approximation of Gaussian probability distributions with a phenomenological ``degeneracy'' factor included. Predictions are compared with data from Monte Carlo simulations of the three-dimensional, $XXZ$ Heisenberg antiferromagnet in a field in order to study the finite-size behavior on a $L\ifmmode\times\else\texttimes\fi{}L\ifmmode\times\else\texttimes\fi{}L$ simple cubic lattice for the first-order ``spin-flop'' transition between the Ising-like antiferromagnetic state and the canted, $XY$-like state. Our theory predicts that for large linear dimension $L$ the field dependen…