2,048 research outputs found
Evidence for the absence of regularization corrections to the partial-wave renormalization procedure in one-loop self energy calculations in external fields
The equivalence of the covariant renormalization and the partial-wave
renormaliz ation (PWR) approach is proven explicitly for the one-loop
self-energy correction (SE) of a bound electron state in the presence of
external perturbation potentials. No spurious correctio n terms to the
noncovariant PWR scheme are generated for Coulomb-type screening potentia ls
and for external magnetic fields. It is shown that in numerical calculations of
the SE with Coulombic perturbation potential spurious terms result from an
improper treatment of the unphysical high-energy contribution. A method for
performing the PWR utilizing the relativistic B-spline approach for the
construction of the Dirac spectrum in external magnetic fields is proposed.
This method is applied for calculating QED corrections to the bound-electron
-factor in H-like ions. Within the level of accuracy of about 0.1% no
spurious terms are generated in numerical calculations of the SE in magnetic
fields.Comment: 22 pages, LaTeX, 1 figur
Toward high-precision values of the self energy of non-S states in hydrogen and hydrogen-like ions
The method and status of a study to provide numerical, high-precision values
of the self-energy level shift in hydrogen and hydrogen-like ions is described.
Graphs of the self energy in hydrogen-like ions with nuclear charge number
between 20 and 110 are given for a large number of states. The self-energy is
the largest contribution of Quantum Electrodynamics (QED) to the energy levels
of these atomic systems. These results greatly expand the number of levels for
which the self energy is known with a controlled and high precision.
Applications include the adjustment of the Rydberg constant and atomic
calculations that take into account QED effects.Comment: Minor changes since previous versio
Recoil correction to the bound-electron g factor in H-like atoms to all orders in
The nuclear recoil correction to the bound-electron g factor in H-like atoms
is calculated to first order in and to all orders in . The
calculation is performed in the range Z=1-100. A large contribution of terms of
order and higher is found. Even for hydrogen, the higher-order
correction exceeds the term, while for uranium it is above the
leading correction.Comment: 6 pages, 3 tables, 1 figur
Solving Medium-Density Subset Sum Problems in Expected Polynomial Time: An Enumeration Approach
The subset sum problem (SSP) can be briefly stated as: given a target integer
and a set containing positive integer , find a subset of
summing to . The \textit{density} of an SSP instance is defined by the
ratio of to , where is the logarithm of the largest integer within
. Based on the structural and statistical properties of subset sums, we
present an improved enumeration scheme for SSP, and implement it as a complete
and exact algorithm (EnumPlus). The algorithm always equivalently reduces an
instance to be low-density, and then solve it by enumeration. Through this
approach, we show the possibility to design a sole algorithm that can
efficiently solve arbitrary density instance in a uniform way. Furthermore, our
algorithm has considerable performance advantage over previous algorithms.
Firstly, it extends the density scope, in which SSP can be solved in expected
polynomial time. Specifically, It solves SSP in expected time
when density , while the previously best
density scope is . In addition, the overall
expected time and space requirement in the average case are proven to be
and respectively. Secondly, in the worst case, it
slightly improves the previously best time complexity of exact algorithms for
SSP. Specifically, the worst-case time complexity of our algorithm is proved to
be , while the previously best result is .Comment: 11 pages, 1 figur
Two-Loop Effects and Current Status of the 4He+ Lamb Shift
We report on recent progress in the treatment of two-loop binding corrections
to the Lamb shift, with a special emphasis on S and P states. We use these and
other results in order to infer an updated theoretical value of the Lamb shift
in 4He+.Comment: 11 pages, nrc1 style; paper presented at PSAS (2006), Venic
Double Beta Decay, Majorana Neutrinos, and Neutrino Mass
The theoretical and experimental issues relevant to neutrinoless double-beta
decay are reviewed. The impact that a direct observation of this exotic process
would have on elementary particle physics, nuclear physics, astrophysics and
cosmology is profound. Now that neutrinos are known to have mass and
experiments are becoming more sensitive, even the non-observation of
neutrinoless double-beta decay will be useful. If the process is actually
observed, we will immediately learn much about the neutrino. The status and
discovery potential of proposed experiments are reviewed in this context, with
significant emphasis on proposals favored by recent panel reviews. The
importance of and challenges in the calculation of nuclear matrix elements that
govern the decay are considered in detail. The increasing sensitivity of
experiments and improvements in nuclear theory make the future exciting for
this field at the interface of nuclear and particle physics.Comment: invited submission to Reviews of Modern Physics, higher resolution
figures available upon request from authors, Version 2 has fixed typos and
some changes after referee report
Energy efficient plasma processing of industrial wastes
The paper presents the results of thermodynamic modeling of the process of joint plasma treatment of non-combustible and combustible industrial wastes. The compositions of water-salt-organic compositions based on these wastes and regimes providing their energy-efficient joint treatment in air plasma have been determined
Inhibiting the coregulator CoREST impairs Foxp3+ Treg function and promotes antitumor immunity
Foxp3+ Tregs are key to immune homeostasis, but the contributions of various large, multiprotein complexes that regulate gene expression remain unexplored. We analyzed the role in Tregs of the evolutionarily conserved CoREST complex, consisting of a scaffolding protein, Rcor1 or Rcor2, plus Hdac1 or Hdac2 and Lsd1 enzymes. Rcor1, Rcor2, and Lsd1 were physically associated with Foxp3, and mice with conditional deletion of Rcor1 in Foxp3+ Tregs had decreased proportions of Tregs in peripheral lymphoid tissues and increased Treg expression of IL-2 and IFN-\u3b3 compared with what was found in WT cells. Mice with conditional deletion of the gene encoding Rcor1 in their Tregs had reduced suppression of homeostatic proliferation, inability to maintain long-term allograft survival despite costimulation blockade, and enhanced antitumor immunity in syngeneic models. Comparable findings were seen in WT mice treated with CoREST complex bivalent inhibitors, which also altered the phenotype of human Tregs and impaired their suppressive function. Our data point to the potential for therapeutic modulation of Treg functions by pharmacologic targeting of enzymatic components of the CoREST complex and contribute to an understanding of the biochemical and molecular mechanisms by which Foxp3 represses large gene sets and maintains the unique properties of this key immune cell
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