49,629 research outputs found

### Collider Jets in Perturbation Theory

Recent progress in the perturbative analysis of hadronic jets, especially in
the context of hadron colliders, is discussed. The characteristic feature of
this work is the emergence of a level of precision in the study of the strong
interactions far beyond that previously possible. Inclusive cross sections for
high energy jets at the Tevatron are now perturbatively calculable with a
reliability on the order of 10%. At present this theoretical precision is
comparable to the quoted experimental errors. Progress has also been made
towards understanding both the internal structure of jets and the influence of
the details of the jet-defining algorithm.Comment: Talk presented at the XXVIIIth Rencontres de Moriond, 1993, LATeX, 13
pages including figures (uu file at end), CERN-TH.6861/9

### The Voyager encounter with Uranus and Neptune

Voyager 2 approaches Uranus at a relative low phase angle and high southerly latitude. Only when the spacecraft is very close to Uranus does the geometry change appreciably. Most of the important observations occur within six hours of closest approach. Voyager flies through an Earth and solar occulation zone and leaves Uranus at a relatively high phase angle of about 145 degrees. There isn't much of an opportunity to look at the equatorial region of the planet. At Neptune, on the other hand, the approach is more nearly equatorial (about 35 deg S lat). Voyager 2 will come much closer to Nepture than to any of the other gas giants as it skims within about 2000 km of Neptune's cloudtops. It will pass through earth and solar occultation zones at both Neptune and its satellite, Triton. Again, Voyager 2 will leave Neptune at about 35 deg S latitude. Voyager operational instrument, interplanetary trajectories and planetary encounters are briefly discussed

### Heavy Quark Production at High Energy

We report on QCD radiative corrections to heavy quark production valid at
high energy. The formulae presented will allow a matched calculation of the
total cross section which is correct at O(\as^3) and includes resummation of
all terms of order \as^3 [\as \ln (s/m^2)]^n. We also include asymptotic
estimates of the effect of the high energy resummation. A complete description
of the calculation of the heavy quark impact factor is included in an appendix.Comment: 32 pages (LaTeX) with three figures. Resubmission to agree with
published version, which contains a new note added in proof and modifications
of text of appendix

### Some Physical Aspects of Liouville String Dynamics

We discuss some physical aspects of our Liouville approach to non-critical
strings, including the emergence of a microscopic arrow of time, effective
field theories as classical ``pointer'' states in theory space, $CPT$ violation
and the possible apparent non-conservation of angular momentum. We also review
the application of a phenomenological parametrization of this formalism to the
neutral kaon system.Comment: CERN-TH.7269/94, 37 pages, 2 figures (not included), latex. Direct
inquiries to: [email protected]

### A Liouville String Approach to Microscopic Time and Cosmology

In the non-critical string framework that we have proposed recently, the time
$t$ is identified with a dynamical local renormalization group scale, the
Liouville mode, and behaves as a statistical evolution parameter, flowing
irreversibly from an infrared fixed point - which we conjecture to be a
topological string phase - to an ultraviolet one - which corresponds to a
static critical string vacuum. When applied to a toy two-dimensional model of
space-time singularities, this formalism yields an apparent renormalization of
the velocity of light, and a $t$-dependent form of the uncertainty relation for
position and momentum of a test string. We speculate within this framework on a
stringy alternative to conventional field-theoretical inflation, and the decay
towards zero of the cosmological constant in a maximally-symmetric space.Comment: Latex 23 pages, no figures, CERN-TH.7000/93, CTP-TAMU-66/9

### Scalar Glueball--Quarkonium Mixing and the Structure of the QCD Vacuum

We use Ward identities of broken scale invariance to infer the amount of
scalar glueball--$\bar{q}q$ meson mixing from the ratio of quark and gluon
condensates in the QCD vacuum. Assuming dominance by a single scalar state, as
suggested by a phase-shift analysis, we find a mixing angle $\gamma \sim
36^{\circ}$, corresponding to near-maximal mixing of the glueball and
$\bar{s}s$ components.Comment: 7 pages, LaTe

### High-temperature constitutive modeling

Thermomechanical service conditions for high-temperature levels, thermal transients, and mechanical loads severe enough to cause measurable inelastic deformation are studied. Structural analysis in support of the design of high-temperature components depends strongly on accurate mathematical representations of the nonlinear, hereditary, inelastic behavior of structural alloys at high temperature, particularly in the relatively small strain range. Progress is discussed in the following areas: multiaxial experimentation to provide a basis for high-temperature multiaxial constitutive relationships; nonisothermal testing and theoretical development toward a complete thermomechanically path dependent formulation of viscoplasticity; and development of viscoplastic constitutive model accounting for initial anisotropy

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