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We apply the technique of self-similar exponential approximants based on successive truncations of simple continued exponentials to reconstruct functional laws of the quasi-exponential class from the knowledge of only a few terms of their power series. Comparison with the standard Padé approximants shows that, in general, the self-similar exponential approximants provide significantly better reconstructions.

We use exact results in a new approach to quantum gravity to study the effect of quantum loop corrections on the behavior of the metric of spacetime near the Schwarzschild radius of a massive point particle in the standard model. We show that the classical conclusion that such a system is a black hole is obviated. Phenomenological implications are discussed.

We use the theory of YFS resummation to compute the size of the expected resummed soft radiative threshold effects in precision studies of heavy particle production at the LHC, where accuracies of 1% are desired in some processes. We find that the soft QED threshold effects are at the level of 0.3% whereas the soft QCD threshold effects enter at the level of 20% and hence both must be controlled to be on the conservative side to achieve such goals.

We show that, by using resummation techniques based on the extension of the methods of Yennie, Frautschi and Suura to Feynman's formulation of Einstein's theory, we get quantum field theoretic predictions for the UV fixed-point values of the dimensionless gravitational and cosmological constants. Connections to the phenomenological asymptotic safety analysis of Planck scale cosmology by Bonanno and Reuter are discussed.

We review the phenomenology of electroweak bosons produced in hadron–hadron collisions. In particular, we discuss the transverse momentum distribution of lepton pairs with invariant mass close to the Z peak. We describe the theoretical calculation for the magnitude of the transverse momentum Q_T and its comparison to Tevatron and LHC data. We also discuss the related variable ϕ*, describing its experimental advantages as well as its relation to the standard Q_T variable. Finally, we compare resummed predictions for ϕ* to data.

In this paper, we consider general relativity in the large N limit, where N stands for the number of particles in the model. Studying the resummed graviton propagator in the linearized regime, we propose to interpret its complex poles as black hole precursors. Our main result is the calculation of the mass and width of the lightest of black holes. We show that the values of the masses of black hole precursors depend on the number of fields in the theory. Their masses can be lowered down to the TeV region by increasing the number of fields in a hidden sector that only interacts gravitationally with the Standard Model.

We present the connection between the running of the cosmological constant and the estimate of its value in the resummed quantum gravity (RQG) realization of quantum general relativity. We also address in this way some of the questions that have been raised concerning this latter generalization and application of the original prescription of Feynman for the formulation of quantum general relativity.

In this paper, we present a general analytic expansion in powers of 1/n of the resonant states of quantum mechanical systems, where n = 1, 2, 3, $\dots$ is the excitation number. Explicit formulas are obtained for some potential barrier models.

We identify a class of perturbatively computable measures of interjet energy flow, which can be associated with well-defined color flow at short distances. As an illustration, we calculate correlations between event shapes and the flow of energy, Q_Ω, into an interjet angular region, Ω, in high-energy two-jet e⁺e^--annihilation events. Laplace transforms with respect to the event shapes suppress states with radiation at intermediate energy scales, so that we may compute systematically logarithms of interjet energy flow. This method provides a set of predictions on energy radiated between jets, as a function of event shape and of the choice of the region Ω in which the energy is measured. Non-global logarithms appear as corrections. We apply our method to a continuous class of event shapes.

We study on-shell decays of light vector meson resonances ρ, K* and ϕ in the framework of chiral constituent quark model using resummation calculations. Such studies are necessary for showing that dynamics described by chiral Lagrangian works well at this energy scale. The effective action is derived by a proper vertex method, where resummation of all orders of momentum expansion is accomplished. Also studied are the loop effects of pseudoscalar meson, which play an important role at this energy scale. The numerical results agree well with the experimental data. A new method to explore the chiral symmetry spontaneously breaking (CSSB) is proposed. It is found that the unitarity of the effective meson theory resulted from resummation derivations demands an upper-limit to the momentum of vector meson. This upper-limit, being critical point, is just the energy scale of CSSB, and is found to be flavor-dependent.

Previous work on soft-gluon resummation for direct photon production is extended to include additional subleading logarithmic terms through and some representative comparisons are made to experimental results from the E-706 and UA-6 Collaborations. The additional terms are small in magnitude, indicating good convergence properties to the level of accuracy calculated. The scale dependence remains much smaller than that of the next-to-leading-order calculation.

We use exact results in a new approach to quantum gravity to discuss some issues in black hole physics.

We present the elements of resummed quantum gravity, a new approach to QG based on the work of Feynman using the simplest example of a scalar field as the representative matter. We show that we get a UV finite quantum correction to Newton's law.

I discuss general unified formulas for resumming collinear and soft contributions to QCD hard scattering cross sections at large x. Expansions of the resummed cross sections to next-to-next-to-next-to-leading order are also shown along with applications of the formalism.

With an eye toward LHC processes in which theoretical precisions of 1% are desired, we introduce the theory of the simultaneous YFS resummation of QED and QCD to compute the size of the expected resummed soft radiative threshold effects in precision studies of heavy particle production at the LHC. Our results show that both QED and QCD soft threshold effects must be controlled to be on the conservative side to achieve such precision goals.

We review the theoretical status of squark and gluino hadroproduction and provide numerical predictions for all squark and gluino pair-production processes at the Tevatron and at the LHC, with a particular emphasis on proton–proton collisions at 7 TeV. Our predictions include next-to-leading order supersymmetric QCD corrections and the resummation of soft gluon emission at next-to-leading-logarithmic accuracy. We discuss the impact of the higher-order corrections on total cross-sections, and provide an estimate of the theoretical uncertainty due to scale variation and the parton distribution functions.

I review calculations of soft-gluon corrections for top-quark production in hadron collisions. I describe theoretical formalisms for their resummation and for finite-order expansions. I show that soft-gluon corrections are dominant for a large number of top-quark processes. I discuss top–antitop pair production as well as single-top production, including total cross sections and differential distributions, and compare with data from the LHC and the Tevatron. I also discuss top-quark production in association with charged Higgs bosons, Z bosons and other particles in models of new physics.

In this review paper, we discuss the influence of weak quenched disorder on the critical behavior in condensed matter and give a brief review of the available experimental and theoretical results as well as results of MC simulations of these phenomena. We concentrate on three cases: (i) uncorrelated random-site disorder, (ii) long-range correlated random-site disorder, and (iii) random anisotropy.

Today, the standard analytical description of critical behavior is given by renormalization group results refined by resummation of the perturbation theory series. The convergence properties of the series are unknown for most disordered models. The main object of this review is to discuss the peculiarities of the application of resummation techniques to perturbation theory series of disordered models.

We use our resummed quantum gravity approach to Einstein's general theory of relativity in the context of the Planck scale cosmology formulation of Bonanno and Reuter to estimate the value of the cosmological constant such that ρ_Λ = (0.0024 eV)⁴. We argue that the closeness of this estimate to experiment constrains Supersymmetric Grand Unified Theory (susy GUT) models. We discuss in turn various theoretical issues that have been raised about the approach itself as well as about the application to estimate the cosmological constant. Given the closeness of the estimate to the currently observed value, we also discuss the theoretical uncertainty in the estimate-at this time, we argue it is still large.

We review the relation between the QCD perturbative resummation and evolution. Particularly we emphasize briefly the idea on how to use the evolution equation to resum the important double logarithms appeared in the perturbative QCD expansion when the process involves two distinctive scales Q₁ ≫ Q₂. We present the resummation formalism for the single transverse spin asymmetry for both semi-inclusive deep inelastic scattering and Drell-Yan production processes.