Open Access. Powered by Scholars. Published by Universities.®

Physical Sciences and Mathematics Commons™

Open Access. Powered by Scholars. Published by Universities.®

University of Massachusetts Amherst

2001

Discipline
Keyword
Publication
Publication Type

Articles 91 - 99 of 99

Full-Text Articles in Physical Sciences and Mathematics

Nucleon Structure And Parity-Violating Electron Scattering, Dh Beck, Br Holstein Jan 2001

Nucleon Structure And Parity-Violating Electron Scattering, Dh Beck, Br Holstein

Physics Department Faculty Publication Series

We review the area of strange quark contributions to nucleon structure. In particular, we focus on current models of strange quark vector currents in the nucleon and the associated parity-violating elastic electron scattering experiments from which vector and axial-vector currents are extracted.

Go to article

The Influence Of Dimension Eight Operators On Weak Matrix Elements, Jf Donoghue Jan 2001

The Influence Of Dimension Eight Operators On Weak Matrix Elements, Jf Donoghue

Physics Department Faculty Publication Series

I describe recent work with V. Cirigliano and E. Golowich on the effect of dimension eight operators on weak nonleptonic amplitudes. The basic mesage is that there is an inconsistency in the way that many calculations are traditionally performed. If one calculates matrix elements involving only physics below some scale μ, then one needs dimension eight operators explicitly in the weak OPE. On the other hand if one wants to use dimensional regularization throughout, then one needs all scales to be included within the matrix element, and this results in the same net effect. A numerical estimate indicates that this …

Go to article

Determination Of <(Pi Pi)I=2/Ohm 7,8/K0 > In The Chiral Limit, V Cirigliano, Jf Donoghue, Eugene Golowich, K Maltman Jan 2001

Determination Of <(Pi Pi)I=2/Ohm 7,8/K0 > In The Chiral Limit, V Cirigliano, Jf Donoghue, Eugene Golowich, K Maltman

Physics Department Faculty Publication Series

We reconsider the dispersive evaluation of the weak matrix elements h()I=2|Q7,8|K0i in the chiral limit. The perturbative matching is accomplished fully within the scheme dependence used in the two loop weak OPE calculations. The effects of dimension eight (and higher dimension) operators are fully accounted for. We perform a numerical determination of the weak matrix elements using our dispersive sum rules fortified by constraints from the classical chiral sum rules. A careful assessment of the attendant uncertainties is given.

Go to article

Accelerating Reinforcement Learning Through The Discovery Of Useful Subgoals, Amy Mcgovern, Andrew G. Barto Jan 2001

Accelerating Reinforcement Learning Through The Discovery Of Useful Subgoals, Amy Mcgovern, Andrew G. Barto

Computer Science Department Faculty Publication Series

An ability to adjust to changing environments and unforeseen circumstances is likely to be an important component of a successful autonomous space robot. This paper shows how to augment reinforcement learning algorithms with a method for automatically discovering certain types of subgoals online. By creating useful new subgoals while learning, the agent is able to accelerate learning on a current task and to transfer its expertise to related tasks through the reuse of its ability to attain subgoals. Subgoals are created based on commonalities across multiple paths to a solution. We cast the task of finding these commonalities as a …

Go to article

The Weak Ope And Dimension-Eight Operators, E Golowich Jan 2001

The Weak Ope And Dimension-Eight Operators, E Golowich

Physics Department Faculty Publication Series

No abstract provided.

Go to article

Critical Temperature Shift In Weakly Interacting Bose Gas, V Kashurnikov, N Prokof'ev, B Svistunov Jan 2001

Critical Temperature Shift In Weakly Interacting Bose Gas, V Kashurnikov, N Prokof'ev, B Svistunov

Physics Department Faculty Publication Series

With a high-performance Monte Carlo algorithm we study the interaction-induced shift of the critical point in weakly interacting three-dimensional |ψ|4 theory (which includes quantum Bose gas). In terms of critical density, nc, mass, m, interaction, U, and temperature, T, this shift is universal: Δnc(T) = -Cm3T2U, the constant C found to be equal to 0.0140±0.0005. For quantum Bose gas with the scattering length a this implies ΔTc/Tc = C0an1/3, with C0 = 1.29±0.05.

Go to article

Critical Point Of A Weakly Interacting Two-Dimensional Bose Gas, N Prokof'ev, O Ruebenacker, B Svistunov Jan 2001

Critical Point Of A Weakly Interacting Two-Dimensional Bose Gas, N Prokof'ev, O Ruebenacker, B Svistunov

Physics Department Faculty Publication Series

We study the Berezinskii-Kosterlitz-Thouless transition in a weakly interacting 2D quantum Bose gas using the concept of universality and numerical simulations of the classical |ψ|4 model on a lattice. The critical density and chemical potential are given by relations nc = (mT/2πħ2)ln(ξħ2/mU) and μc = (mTU/πħ2)ln(ξμħ2/mU), where T is the temperature, m is the mass, and U is the effective interaction. The dimensionless constant ξ = 380±3 is very large and thus any quantitative analysis of the experimental data crucially depends on its value. For ξμ our result is ξμ = 13.2±0.4. We also report the study of the quasicondensate …

Go to article

Bilinear Operators With Non-Smooth Symbol, I, John E. Gilbert, Andrea R. Nahmod Jan 2001

Bilinear Operators With Non-Smooth Symbol, I, John E. Gilbert, Andrea R. Nahmod

Mathematics and Statistics Department Faculty Publication Series

This paper proves the Lp-boundedness of general bilinear operators associated to a symbol or multiplier which need not be smooth. The Main Theorem establishes a general result for multipliers that are allowed to have singularities along the edges of a cone as well as possibly at its vertex. It thus unifies ealier results of Coifman-Meyer for smooth multipliers and ones, such the Bilinear Hilbert transform of Lacey-Thiele, where the multiplier is not smooth. Using a Whitney decomposition in the Fourier plane a general bilinear operator is represented as infinite discrete sums of time-frequency paraproducts obtained by associating wave-packets with tiles …

Go to article

Complementary Algorithms For Tableaux, Tom Roby, Frank Sottile, Jeff Stroomer, Julian West Jan 2001

Complementary Algorithms For Tableaux, Tom Roby, Frank Sottile, Jeff Stroomer, Julian West

Mathematics and Statistics Department Faculty Publication Series

We study four operations defined on pairs of tableaux. Algorithms for the first three involve the familiar procedures of jeu de taquin, row insertion, and column insertion. The fourth operation, hopscotch, is new, although specialised versions have appeared previously. Like the other three operations, this new operation may be computed with a set of local rules in a growth diagram, and it preserves Knuth equivalence class. Each of these four operations gives rise to an a priori distinct theory of dual equivalence. We show that these four theories coincide. The four operations are linked via the involutive tableau operations of …

Go to article

First Prev