Multi-matrix models and genus one amplitudes

The genus one correlation numbers in the matrix models and the minimal Liouville gravity have been studied. The torus partition function for the matrix models, as well as the one- and two-point correlation numbers of the (3, p) matrix models and (3, p) minimal Liouville gravity, has been calculated.     

Multi-matrix vector coherent states

A class of vector coherent states is derived with multiple of matrices as vectors in a Hilbert space, where the Hilbert space is taken to be the tensor product of several other Hilbert spaces. As examples vector coherent states with multiple of quaternions and octonions are given. The resulting generalized oscillator algebra is briefly discussed. Further, vector coherent states for a tensored Hamiltonian system are obtained by the same method. As particular cases, coherent states are obtained for tensored Jaynes-Cummings type Hamiltonians and for a two-level two-mode generalization of the Jaynes-Cummings model.     

Jittering wave-packet models for subsonic jet noise

Three simplified wave-packet models of the coherent structures in subsonic jets are presented. The models comprise convected wave-packets with time-dependent amplitudes and spatial extents. The dependence of the radiated sound on the temporal variations of the amplitude and spatial extent of the modulations are studied separately in the first two model problems, being considered together in the third. Analytical expressions for the radiated sound pressure are obtained for the first and third models.Results show that temporally localised changes in the wave-packet can lead to radiation patterns which are directional and which comprise high-amplitude bursts; such intermittency is observed in subsonic jets at the end of the potential core, and so the models may help explain the higher noise levels and intermittent character of the sound radiated to low emission angles for subsonic jets. By means of an efficiency metric, relating the radiated acoustic power to the fluctuation energy of the source, we show that the source becomes more powerful as its temporal localisation is increased. This result extends that of Sandham et al. (Journal of Sound and Vibration 294(1) (2006) 355–361) who found similar behaviour for an infinitely extended wavy-wall.The pertinence of the model is assessed using two sets of data for a Mach 0.9 jet. One corresponds to a direct numerical simulation (DNS) of a Reynolds number 3600 turbulent jet and the other to a large eddy simulation (LES) of a Reynolds number 4×10⁵ jet. Both time-averaged and time-dependent amplitudes and spatial extents are extracted from the velocity field of the numerical data. Computing the sound field generated by the wave-packet models we find for both simulations that while the wave-packet with a time-averaged envelope shows discrepancies of more than an order of magnitude with the sound field, when the wave-packet ‘jitters’ in a way similar to the intermittency displayed by the simulations, we obtain agreement to within 1.5 dB at low axial angles. This shows that the ‘jitter’ of the wave-packet is a salient source feature, and one which should be modelled explicitly.     

Determination of the kinetic coefficients of a gas in a supersonic jet from Brillouin spontaneous scattering spectra

The mean free path and the shear viscosity of molecular nitrogen are determined in a rarefied supersonic jet using the Brillouin spontaneous scattering technique. By examples of sub-and supersonic jets, the measured kinetic coefficients are shown to agree with the tabulated values of these parameters. These results are obtained using laser radiation, whose output power, which restricts the signal-to-noise ratio, is as low as 50 mW.     

Some comments on jet fragmentation models andα s determinations

A number of interrelated topics on jet properties ine ⁺ e ^? annihilation is discussed. The need for differentα _s values in different fragmentation models is explained, with particular emphasis on the sensitivity to the choice of momentum conservation scheme in independent fragmentation models. Also other factors leading to a broad range of experimentalα _s values are discussed. Old and new methods to distinguish different fragmentation models are presented, with particular emphasis on gluon jet fragmentation properties.     

Hadronic structure from jet physics

We discuss some aspects of high p_T jet physics, which are particularly relevant to test QCD and to probe the quark and gluon structure of hadrons. These include the so-called minijets, the multiple parton process, and the hard diffractive production.Invited talk at the International Symposium Hadron interactions — Theory and Pnenomenology, Bechyn, Czechoslovakia, June 26–July 1, 1988.     

Resonance production from jet fragmentation

Short lived resonances are sensitive to the medium properties in heavy-ion collisions. Heavy hadrons have larger probability to be produced within the quark gluon plasma phase due to their short formation times. Therefore heavy mass resonances are more likely to be affected by the medium, and the identification of early produced resonances from jet fragmentation might be a viable option to study chirality. The high momentum resonances on the away-side of a triggered di-jet are likely to be the most modified by the partonic or early hadronic medium. We will discuss first results of triggered hadron-resonance correlations in Cu+Cu heavy ion collisions.     

Asymmetric glottal jet deflection: differences of two- and three-dimensional models

Flow is studied through a channel with an oscillating orifice mimicking the motion of the glottal-gap during phonation. Simulations with prescribed flow and wall-motion are carried out for different orifice geometries, a 2D slit-like and a 3D lens-like one. Although the jet emerges from a symmetric orifice a significant deflection occurs in case of the slit-like geometry, contrary to the 3D lens-like one. The results demonstrate the dependency of jet entrainment and vortex dynamics on the orifice geometry and the interpretation of asymmetric jet deflection with regard to the relevance of the Coanda effect in the process of human phonation.     

Astrophysical S-factors from asymptotic normalization coefficients

S-factors for direct capture reactions can be found at astrophysical energies from asymptotic normalization coefficients which provide the normalization of the tail of the overlap function. For example the overlap for ⁸B → ⁷Be+p defines the S-factor for ⁷Be (p, γ)⁸B. Peripheral transfer reactions offer a technique to determine these asymptotic normalization coefficients. As a test of the technique, the ¹⁶O(³He, d)¹⁷F reaction has been used to determine asymptotic normalization coefficients for transitions to the ground and first excited states of ¹⁷F. The S-factors for ¹⁶O(p, γ)¹⁷F calculated from these ¹⁷F → ¹⁶O+p asymptotic normalization coefficients are found to be in very good agreement with recent measurements. Following the same technique, the ¹⁰B(⁷Be, ⁸B)⁹Be and ¹⁴N(⁷Be, ⁸B)¹³C reactions have been used to measure the asymptotic normalization coefficient for ⁷Be(p, γ)⁸B. This result provides an indirect determination of S ₁₇(0).     

Evaluation of second and third dielectric virial coefficients for non-polarisable molecular models

The dielectric constant, ε, of a dilute vapour can be estimated from the dielectric virial equation of state (VEOS), but the long-ranged nature of the electrostatic interactions complicates the evaluation of coefficients of this series. We propose a formulation of the second and third dielectric coefficients of a general non-polarisable molecular model that permits their reliable calculation using Mayer sampling Monte Carlo. We demonstrate for three models: dipolar hard spheres, dipolar Lennard–Jones, and TIP4P water. The coefficients are used to compute ε for each model as a function of density, which are compared to molecular-simulation data. The form of the VEOS relating ε to density depends on the dielectric constant ε′ of the embedding medium. Three choices are examined: vacuum (ε′ = 1), self-consistent (ε′ = ε) and tin foil (ε′ = ∞). The vacuum-boundary form is found to be unreliable, losing accuracy at low density and yielding divergent results for ε at moderate densities. In contrast, the series formulated using the tin-foil boundary produces accurate and stable values of ε for almost all conditions and models examined here, even when truncated at second order (which itself is shown to be a large improvement over the first-order Clausius–Mossotti–Debye formula).     

Relationship between the classical transport coefficients and hydrodynamic kernels for quantum-field models

A study is made of the classical limit of nonlocal hydrodynamics, describing quantum systems of many particles. The quantum-field model is not specified, it being assumed only that there are local laws governing the conservation of energy — momentum and the number of particles. Changing over to the classical limit corresponds in nonlocal hydrodynamics to the limit of slow processes and long waves. It is shown that a hydrodynamics with viscosity and self-diffusion but without heat conduction is obtained in this case because the velocity of the medium is determined in terms of the energy flux, which is natural for quantum-field systems. Heat conduction can be introduced if velocity is instead determined in terms of particle flux. Institute of Earth Physics, Russian Academy of Sciences. Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika No. 8, pp. 61–66, August, 1996.     

Zernike aberration coefficients transformed to and from Fourier series coefficients for wavefront representation

The set of Fourier series is discussed following some discussion of Zernike polynomials. Fourier transforms of Zernike polynomials are derived that allow for relating Fourier series expansion coefficients to Zernike polynomial expansion coefficients. With iterative Fourier reconstruction, Zernike representations of wavefront aberrations can easily be obtained from wavefront derivative measurements.     

Radiation from a source near a jet

The problem examined is that of analysing the field of sound radiation caused due to the presence of a source in the immediate neighbourhood of a cylindrical jet in motion. The general analysis is restricted to low Mach number flow and special consideration is given to the high and low frequency limiting behaviour of the sound in the far field. The reflexion coefficient obtained in the high frequency case is exactly the same as that obtained by previous investigators for a source in the neighbourhood of an interface in relative motion [1, 2]. Also predicted here, however, is the existence of a “zone of excess attenuation” surrounding the jet fluid in motion, on both sides, far beyond the location of the acoustic source.     

Out of medium fragmentation from long-lived jet showers

We study the time structure of vacuum jet evolution via a simple uncertainty principle estimate in the kinematic range explored by current heavy ion collisions at the LHC. We observe that a large fraction of the partonic splittings occur at large times, of the order of several fm. We compare the time distribution of vacuum splittings with the distribution of path lengths traversed by jets in a heavy ion collision. We find that if no medium induced modification of the jet dynamics were present, a very large fraction (larger than 80% for inclusive jets) of the jet splittings would occur outside of the medium. We confront this observation with current available data on jet properties in heavy ion collisions and discuss its implications for the dynamics of jet–medium interactions.     

Finite size effects on transport coefficients for models of atomic wires coupled to phonons

We consider models of quasi-1-d, planar atomic wires consisting of several, laterally coupled rows of atoms, with mutually non-interacting electrons. This electronic wire system is coupled to phonons, corresponding, e.g., to some substrate. We aim at computing diffusion coefficients in dependence on the wire widths and the lateral coupling. To this end we firstly construct a numerically manageable linear collision term for the dynamics of the electronic occupation numbers by following a certain projection operator approach. By means of this collision term we set up a linear Boltzmann equation. A formula for extracting diffusion coefficients from such Boltzmann equations is given. We find in the regime of a few atomic rows and intermediate lateral coupling a significant and non-trivial dependence of the diffusion coefficient on both, the width and the lateral coupling. These results, in principle, suggest the possible applicability of such atomic wires as electronic devices, such as, e.g., switches.     

Prediction of jet noise in flight from static tests

The sound intensity of jet noise from aircraft in flight is derived in a co-ordinate system fixed to the jet engine. For this reason a convected form of the Lighthill equation is solved, with special care taken of jet temperature effects. Under certain assumptions and approximations, the in-flight and static sound intensities are related in a simple manner. Thus the directivity of jet noise in flight can be predicted. The theoretical result is checked with measurements. The agreement is remarkably good.     

Lund jet images from generative and cycle-consistent adversarial networks

The European Physical Journal C - The inclusive hadroproduction of two heavy quarks, featuring a large separation in rapidity, is proposed as a novel probe channel of the...     

High-p t and jet physics from RHIC to LHC

The observation of the strong suppression of high-p t hadrons in heavy-ion collisions at the Relativistic Heavy Ion Collider (RHIC) at BNL has motivated a large experimental program using hard probes to characterize the deconfined medium created. However, what can be denoted as “leading particle” physics accessible at RHIC presents some limitations which motivate at higher energy the study of much more penetrating objects: jets. The gain in center-of-mass energy expected at the Large Hadron Collider (LHC) at CERN will definitively improve our understanding on how the energy is lost in the system, opening a major new window of study: the physics of jets on an event-by-event basis. We will concentrate on the expected performance for jet reconstruction in ALICE using the EMCal calorimeter. (for the ALICE Collaboration) The text was submitted by the author in English.