409 research outputs found
The light-cone gauge and the calculation of the two-loop splitting functions
We present calculations of next-to-leading order QCD splitting functions,
employing the light-cone gauge method of Curci, Furmanski, and Petronzio (CFP).
In contrast to the `principal-value' prescription used in the original CFP
paper for dealing with the poles of the light-cone gauge gluon propagator, we
adopt the Mandelstam-Leibbrandt prescription which is known to have a solid
field-theoretical foundation. We find that indeed the calculation using this
prescription is conceptionally clear and avoids the somewhat dubious
manipulations of the spurious poles required when the principal-value method is
applied. We reproduce the well-known results for the flavour non-singlet
splitting function and the N_C^2 part of the gluon-to-gluon singlet splitting
function, which are the most complicated ones, and which provide an exhaustive
test of the ML prescription. We also discuss in some detail the x=1 endpoint
contributions to the splitting functions.Comment: 41 Pages, LaTeX, 8 figures and tables as eps file
Next-to-leading order Calculation of a Fragmentation Function in a Light-Cone Gauge
The short-distance coefficients for the color-octet ^3S_1 term in the
fragmentation function for a gluon to split into polarized heavy quarkonium
states are re-calculated to order alpha_s^2. The light-cone gauge remarkably
simplifies the calculation by eliminating many Feynman diagrams at the expense
of introducing spurious poles in loop integrals. We do not use any conventional
prescriptions for spurious pole. Instead, we only use gauge invariance with the
aid of Collins-Soper definition of the fragmentation function. Our result
agrees with a previous calculation of Braaten and Lee in the Feynman gauge, but
disagrees with another previous calculation.Comment: 16 pages, 4 figures, version published in Physical Review
Finite temperature formalism for nonabelian gauge theories in the physical phase space
We establish a new framework of finite temperature field theory for
Yang-Mills theories in the physical phase space eliminating all unphysical
degrees of freedoms. Relating our method to the imaginary time formalism of
James and Landshoff in temporal axial gauge, we calculate the two-loop pressure
and provide a systematic and unique method to construct the additional vertices
encountered in their approach.Comment: 18 pages, 5 postscript figures, uses revtex, eps
Do Competitive Work Places Deter Female Workers? A Large-Scale Natural Field Experiment on Gender Differences in Job-Entry Decisions
Recently an important line of research using laboratory experiments has provided a new potential reason for why we observe gender imbalances in labor markets: men are more competitively inclined than women. Whether, and to what extent, such preferences yield differences in naturally-occurring labor market outcomes remains an open issue. We address this question by exploring job-entry decisions in a natural field experiment where we randomized nearly 7,000 interested job-seekers into different compensation regimes. By varying the role that individual competition plays in setting the wage, we are able to explore whether competition, by itself, can cause differential job entry. The data highlight the power of the compensation regime in that women disproportionately shy away from competitive work settings. Yet, there are important factors that attenuate the gender differences, including whether the job is performed in teams, whether the job task is female-oriented, and the local labor market.
Gauge Invariance and Anomalous Dimensions of a Light-Cone Wilson Loop in Light-Like Axial Gauge
Complete two-loop calculation of a dimensionally regularized Wilson loop with
light-like segments is performed in the light-like axial gauge with the
Mandelstam-Leibbrandt prescription for the gluon propagator. We find an
expression which {\it exactly} coincides with the one previously obtained for
the same Wilson loop in covariant Feynman gauge. The renormalization of Wilson
loop is performed in the \MS-scheme using a general procedure tailored to the
light-like axial gauge. We find that the renormalized Wilson loop obeys a
renormalization group equation with the same anomalous dimensions as in
covariant gauges. Physical implications of our result for investigation of
infrared asymptotics of perturbative QCD are pointed out.Comment: 24 pages and 4 figures (included), LaTeX style, UFPD-93/TH/23,
UPRF-93-366, UTF-93-29
Increasing Workplace Diversity: Evidence from a Recruiting Experiment at a Fortune 500 Company
While many firms have set ambitious goals to increase diversity in their ranks, there is a dearth of empirical evidence on effective ways to reach them. We use a natural field experiment to test several hypotheses on effective meansto attract minority candidates for top professional careers. By randomly varying the content in recruiting materials of a major financial services corporation with more than 10,000 employees, we find that signaling explicit interest in employee diversity more than doubles the interest in openings among racial minority candidates, as well as the likelihood that they apply and are selected. Impacts on gender diversity are less sharp and generally not significan
Wilson Loop and the Treatment of Axial Gauge Poles
We consider the question of gauge invariance of the Wilson loop in the light
of a new treatment of axial gauge propagator proposed recently based on a
finite field-dependent BRS (FFBRS) transformation. We remark that as under the
FFBRS transformation the vacuum expectation value of a gauge invariant
observable remains unchanged, our prescription automatically satisfies the
Wilson loop criterion. Further, we give an argument for {\it direct}
verification of the invariance of Wilson loop to O(g^4) using the earlier work
by Cheng and Tsai. We also note that our prescription preserves the thermal
Wilson loop to O(g^2).Comment: 8 pages, LaTex; some typos related to equation (18) correcte
Comparison of quantum field perturbation theory for the light front with the theory in lorentz coordinates
The relationship between the perturbation theory in light-front coordinates
and Lorentz-covariant perturbation theory is investigated. A method for finding
the difference between separate terms of the corresponding series without their
explicit evaluation is proposed. A procedure of constructing additional
counter-terms to the canonical Hamiltonian that compensate this difference at
any finite order is proposed. For the Yukawa model, the light-front Hamiltonian
with all of these counter-terms is obtained in a closed form. Possible
application of this approach to gauge theories is discussed.Comment: LaTex 2.09, 20 pages, 5 figure
Thermal one- and two-graviton Green's functions in the temporal gauge
The thermal one- and two-graviton Green's function are computed using a
temporal gauge. In order to handle the extra poles which are present in the
propagator, we employ an ambiguity-free technique in the imaginary-time
formalism. For temperatures T high compared with the external momentum, we
obtain the leading T^4 as well as the subleading T^2 and log(T) contributions
to the graviton self-energy. The gauge fixing independence of the leading T^4
terms as well as the Ward identity relating the self-energy with the one-point
function are explicitly verified. We also verify the 't Hooft identities for
the subleading T^2 terms and show that the logarithmic part has the same
structure as the residue of the ultraviolet pole of the zero temperature
graviton self-energy. We explicitly compute the extra terms generated by the
prescription poles and verify that they do not change the behavior of the
leading and sub-leading contributions from the hard thermal loop region. We
discuss the modification of the solutions of the dispersion relations in the
graviton plasma induced by the subleading T^2 contributions.Comment: 17 pages, 5 figures. Revised version to be published in Phys. Rev.
Early copper metallurgy in Northern Chile
The Central Andean region of South America has a long tradition of mining and metallurgy. Such activities were fundamental to the economic, socio-political and ideological dynamics of the pre-Columbian cultures that inhabited this area. In spite of their importance, few archaeological investigations of metallurgy have been carried out in the Central Andes in general, and in current Chilean territory in particular. The present project investigates archaeometallurgical sites in northern Chile using scientific analysis, as a first step towards a large-scale map of prehistoric copper production and exchange across South America. This research involves documentation and sampling of already excavated archaeological materials from a number of copper-producing sites located in the Atacama District. Preliminary results of XRF analysis of artefacts from the collection of the R. P. Gustavo Le Paige Archaeological Museum, San Pedro de Atacama, have been obtained and enabled us to characterise the different elements present in the metal objects. These results might provide information on the nature of the raw materials used
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