119738846
Two-beam detuned-cavity electron accelerator structure
Progress has been made in the theory, development, cavity design and optimization, beam dynamics study, beam transport design, and hardware construction for studies of a detuned two-beam electron accelerator structure.
55339745
Multi-Harmonic Cavity for RF Breakdown Studies
An axially-asymmetric cavity to support several modes at harmonically-related frequencies is predicted to sustain higher RF breakdown thresholds than a conventional pillbox cavity, when driven by two or more external RF phase-locked harmonic sources. Experimental efforts are underway at Yale Beam Physics Lab to study RF breakdown in a bimodal asymmetric cavity. Such a cavity could be a basic building-block for a future high-gradient warm accelerator structure.
110779089
Multi-harmonic RF test stand for RF breakdown studies
A multi-harmonic RF test stand is under construction at Yale Beam Physics Laboratory. It includes a frequency multiplier which can generate high power harmonics efficiently that are phase locked to the fundamental drive frequency. In a bi-modal asymmetric cavity powered by this RF source, the cavity may experience reduced exposure time to peak fields and sweeping of peak fields across their surfaces, and strong asymmetry between surfaces that may experience cathode-and anode-like fields; these phenomena are to be assessed for their influence on RF breakdown probabilities.
119484972
Multi-harmonic test setup for RF breakdown studies
A multi-harmonic asymmetric cavity is predicted to obtain lower RF breakdown probability than a conventional pillbox cavity, when driven by two or more external RF harmonic sources. Experimental efforts are underway to study RF breakdown in a bimodal asymmetric cavity powered by dual frequency test stand. Details of design of the test stand are described.
119251577
Calculation of the staggered spin correlation in the framework of the Dyson-Schwinger approach
Based on the linear response of the fermion propagator with respect to an external field, we first derive a model-independent expression for the staggered spin susceptibility in which the influence of the full pseudoscalar vertex function is included. This expression for the staggered spin susceptibility is quite different from that given in the previous literature. The numerical values of the staggered spin susceptibility are calculated within the framework of the Dyson-Schwinger approach. Our numerical result shows that the nonperturbative dressing effects on the fermion propagator are very important when one studies the staggered spin susceptibility corresponding to the antiferromagnetic correlation in both the Nambu phase and Wigner phase.
118489624
Calculation of bulk viscosity of QCD at zero temperature and finite chemical potential
In this paper, based on Kubo's formula and the QCD low energy theorem, we propose a direct formula for calculating the bulk viscosity of QCD at finite chemical potential μ and zero temperature. According to this formula, the bulk viscosity at finite μ is totally determined by the dressed quark propagator at finite μ. We then use a dynamical, confining Dyson–Schwinger equation model of QCD to calculate the bulk viscosity at finite μ. It is found that no sharp peak behavior of the bulk viscosity at finite μ is observed, which is quite different from that of the bulk viscosity at finite temperature.
4807800
Fixing the quantum three-point function
A bstractWe propose a new method for the computation of quantum three-point functions for operators in $ \mathfrak{s}\mathfrak{u} $(2) sectors of $ \mathcal{N} $ = 4 super Yang-Mills theory. The method is based on the existence of a unitary transformation relating inhomogeneous and long-range spin chains. This transformation can be traced back to a combination of boost operators and an inhomogeneous version of Baxter’s corner transfer matrix. We reproduce the existing results for the one-loop structure constants in a simplified form and indicate how to use the method at higher loop orders. Then we evaluate the one-loop structure constants in the quasiclassical limit and compare them with the recent strong coupling computation.
119190000
Wigner solution of the quark gap equation at nonzero current quark mass and partial restoration of chiral symmetry at finite chemical potential
According to the generally accepted phase diagram of QCD, at low temperature and high baryon number density the chiral phase transition of QCD is of first order and the co-existence of the Nambu-Goldstone phase and the Wigner phase should appear. This is in conflict with the usual claim that the quark gap equation has no Wigner solution in the case of nonzero current quark mass. In this paper we analyze the reason why the Wigner solution does not exist in the usual treatment and try to propose a new approach to discuss this question. As a first step, we adopt a modified Nambu-Jona-Lasinio (NJL) model to study the Wigner solution at finite current quark mass. We then generalize this approach to the case of finite chemical potential and discuss partial restoration of chiral symmetry at finite chemical potential and compare our results with those in the normal NJL model.
124816809
Toric sheaves on weighted projective planes
We give an explicit description of toric sheaves on the weighted projective plane P(a, b, c) viewed as a toric Deligne-Mumford stack. The stack P(a, b, c) has an action of the torus T = C and by a toric sheaf we mean a coherent sheaf together with a lift of the torus action. The integers (a, b, c) are not necessarily chosen coprime or mutually coprime allowing for gerbe and root stack structures. This is a first step in an attempt to give an explicit description of toric sheaves on any smooth toric Deligne-Mumford stack. Specializing the description to torsion free sheaves gives a combinatorial picture with various new features, which do not appear in the case of smooth toric varieties. As an application, we describe the fixed point locus of the moduli scheme of stable rank 1 and 2 torsion free sheaves on P(a, b, c) with fixed K-group class. Summing over all K-group classes, we obtain formulae for generating functions of the topological Euler characteristics of these moduli schemes.