2,156 research outputs found
The three-loop cusp anomalous dimension in QCD
We present the full analytic result for the three-loop angle-dependent cusp
anomalous dimension in QCD. With this result, infrared divergences of planar
scattering processes with massive particles can be predicted to that order.
Moreover, we define a closely related quantity in terms of an effective
coupling defined by the light-like cusp anomalous dimension. We find evidence
that this quantity is universal for any gauge theory, and use this observation
to predict the non-planar -dependent terms of the four-loop cusp
anomalous dimension.Comment: 5 pages, 2 figure
The terms of the three-loop cusp anomalous dimension in QCD
In this talk we present the result for the dependent piece of the
three-loop cusp anomalous dimension in QCD. Remarkably, it is parametrized by
the same simple functions appearing in analogous anomalous dimensions in
SYM at one and two loops. We also compute all required master
integrals using a recently proposed refinement of the differential equation
method. The analytic results are expressed in terms of harmonic polylogarithms
of uniform weight.Comment: 8 pages, 2 figures; v2: typo in eq. (4.4) fixed, 'three-loop' added
to titl
The parameter at three loops and elliptic integrals
We describe the analytic calculation of the master integrals required to
compute the two-mass three-loop corrections to the parameter. In
particular, we present the calculation of the master integrals for which the
corresponding differential equations do not factorize to first order. The
homogeneous solutions to these differential equations are obtained in terms of
hypergeometric functions at rational argument. These hypergeometric functions
can further be mapped to complete elliptic integrals, and the inhomogeneous
solutions are expressed in terms of a new class of integrals of combined
iterative non-iterative nature.Comment: 14 pages Latex, 7 figures, to appear in the Proceedings of "Loops and
Legs in Quantum Field Theory - LL 2018", 29 April - 4 May 2018, Po
Completely automated computation of the heavy-fermion corrections to the three-loop matching coefficient of the vector current
We evaluate the corrections to the matching coefficient of the vector current
between Quantum Chromodynamics (QCD) and Non-Relativistic QCD (NRQCD) to
three-loop order containing a closed heavy-fermion loop. The result constitutes
a building block both for the bottom- and top-quark system at threshold. Strong
emphasis is put on our completely automated approach of the calculation
including the generation of the Feynman diagrams, the identification of the
topologies, the reduction to master integrals and the automated numerical
computation of the latter.Comment: 14 page
Perturbative dynamics of matrix string for the membrane
Recently Sekino and Yoneya proposed a way to regularize the world volume
theory of membranes wrapped around by matrices and showed that one
obtains matrix string theory as a regularization of such a theory. We show that
this correspondence between matrix string theory and wrapped membranes can be
obtained by using the usual M(atrix) theory techniques. Using this
correspondence, we construct the super-Poincare generators of matrix string
theory at the leading order in the perturbation theory. It is shown that these
generators satisfy 10 dimensional super-Poincar\'e algebra without any anomaly.Comment: 23 pages, 1 figur
Single-artificial-atom lasing using a voltage-biased superconducting charge qubit
We consider a system composed of a single artificial atom coupled to a cavity
mode. The artificial atom is biased such that the most dominant relaxation
process in the system takes the atom from its ground state to its excited
state, thus ensuring population inversion. A recent experimental manifestation
of this situation was achieved using a voltage-biased superconducting charge
qubit. Even under the condition of `inverted relaxation', lasing action can be
suppressed if the `relaxation' rate is larger than a certain threshold value.
Using simple transition-rate arguments and a semiclassical calculation, we
derive analytic expressions for the lasing suppression condition and the state
of the cavity in both the lasing and suppressed-lasing regimes. The results of
numerical calculations agree very well with the analytically derived results.
We start by analyzing a simplified two-level-atom model, and we then analyze a
three-level-atom model that should describe accurately the recently realized
superconducting artificial-atom laser.Comment: 21 pages in preprint format, 6 figure
Matching QCD and HQET heavy-light currents at three loops
We consider the currents formed by a heavy and a light quark within Quantum
Chromodynamics and compute the matching to Heavy Quark Effective Theory to
three-loop accuracy. As an application we obtain the third-order perturbative
corrections to ratios of B-meson decay constants.Comment: 23 pages, full results are available as Mathematica files at
http://www-ttp.particle.uni-karlsruhe.de/Progdata/ttp09/ttp09-41/ ; v2: an
error in comparison with Ref. [8] fixed ; v3: Journal versio
Relation between the pole and the minimally subtracted mass in dimensional regularization and dimensional reduction to three-loop order
We compute the relation between the pole quark mass and the minimally
subtracted quark mass in the framework of QCD applying dimensional reduction as
a regularization scheme. Special emphasis is put on the evanescent couplings
and the renormalization of the epsilon-scalar mass. As a by-product we obtain
the three-loop on-shell renormalization constants Zm(OS) and Z2(OS) in
dimensional regularization and thus provide the first independent check of the
analytical results computed several years ago.Comment: 22 page
Reproduction, body condition, age, and growth of a large sandy intertidal bivalve, Tivela stultorum
The iconic Pismo clam Tivela stultorum (Mawe, 1823) once supported a thriving commercial and recreational fishery in California, but populations have declined statewide in recent decades, in part due to overfishing. To manage and restore populations, fishery managers need accurate life history information, but critical data on reproductive cycles, maturity, and growth rates is either unknown or many decades old. This project aimed to (1) determine annual reproductive cycles and body condition of Pismo clams; (2) identify environmental drivers of reproduction and body condition; (3) determine size-age relationships among clams in California; and (4) estimate growth rates. Up to 70 clams mo-1 were collected from Pismo Beach, CA, for histological analysis to determine reproductive stage, measure a body condition index, and estimate ages from shells. Additional clams and shells were collected from sites north and south of Point Conception to compare growth and age at legal size between these 2 major oceanographic zones. Data suggests that reproductive timing deviates only slightly from historical records, with clams spawning later in the year than decades ago. Body condition indices correlate with reproductive stage 3 Ripe, providing an inexpensive proxy to monitor Pismo clam reproduction. Growth was faster in warmer Southern California compared to Central California, but still substantially slower than historical estimates; we estimate that Pismo clams reach the current legal size (114 mm) in 11.1 yr, several years later than previous estimates. Collectively, these data are critical to improve and guide management decisions for this once-abundant species
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