11,815 research outputs found
A DEIM Induced CUR Factorization
We derive a CUR matrix factorization based on the Discrete Empirical
Interpolation Method (DEIM). For a given matrix , such a factorization
provides a low rank approximate decomposition of the form ,
where and are subsets of the columns and rows of , and is
constructed to make a good approximation. Given a low-rank singular value
decomposition , the DEIM procedure uses and to
select the columns and rows of that form and . Through an error
analysis applicable to a general class of CUR factorizations, we show that the
accuracy tracks the optimal approximation error within a factor that depends on
the conditioning of submatrices of and . For large-scale problems,
and can be approximated using an incremental QR algorithm that makes one
pass through . Numerical examples illustrate the favorable performance of
the DEIM-CUR method, compared to CUR approximations based on leverage scores
Discovery and Assessment of New Target Sites for Anti-HIV Therapies
Human immunodeficiency virus (HIV) infects cells by endocytosis and takes over parts of the cell’s reaction pathways in order to reproduce itself and spread the infection. One such pathway taken over by HIV becomes the inflammatory pathway which uses Nuclear Factor κB (NF-κB) as the principal transcription factor. Therefore, knocking out the NF-κB pathway would prevent HIV from reproducing itself. In this report, our goal is to produce a simple model for this pathway with which we can identify potential targets for anti-HIV therapies and test out various hypotheses. We present a very simple model with four coupled first-order ODEs and see what happens if we treat IκK concentration as a parameter that can be controlled (by some unspecified means). In Section 3, we augment this model to account for activation and deactivation of IκK, which is controlled (again, by some unspecified means) by TNF
Effect of resonance decays on hadron elliptic flows
The influence of resonance decays on the elliptic flows of stable hadrons is
studied in the quark coalescence model. Although difference between the
elliptic flow of pions from resonance decays, except the rho meson, and that of
directly produced pions is appreciable, those for other stable hadrons are
small. Since there are more pions from the decays of rho mesons than from other
resonances, including resonance decays can only account partially the deviation
of final pion elliptic flow from the observed scaling of hadron elliptic flows,
i.e., the hadron elliptic flow per quark is the same at same transverse
momentum per quark. The remaining deviation can be explained by including the
effect due to the quark momentum distribution inside hadrons.Comment: 13 pages and 5 figures, version pubblished in PRC, updated references
and figure
Herding cats: observing live coding in the wild
After a momentous decade of live coding activities, this paper seeks to explore the practice with the aim of situating it in the history of contemporary arts and music. The article introduces several key points of investigation in live coding research and discusses some examples of how live coding practitioners engage with these points in their system design and performances. In the light of the extremely diverse manifestations of live coding activities, the problem of defining the practice is discussed, and the question raised whether live coding will actually be necessary as an independent category
Information transfer through a one-atom micromaser
We consider a realistic model for the one-atom micromaser consisting of a
cavity maintained in a steady state by the streaming of two-level Rydberg atoms
passing one at a time through it. We show that it is possible to monitor the
robust entanglement generated between two successive experimental atoms passing
through the cavity by the control decoherence parameters. We calculate the
entanglement of formation of the joint two-atom state as a function of the
micromaser pump parameter. We find that this is in direct correspondence with
the difference of the Shannon entropy of the cavity photons before and after
the passage of the atoms for a reasonable range of dissipation parameters. It
is thus possible to demonstrate information transfer between the cavity and the
atoms through this set-up.Comment: Revtex, 5 pages, 2 encapsulated ps figures; added discussion on
information transfer in relation with cavity photon statistics; typos
corrected; Accepted for Publicaiton in Europhysics Letter
Moment Analysis of the Cluster-Size-Distribution Approach to Scaling During Coagulation
We study the temporal approach of a cluster size distribution to its asymptotic scaling form. By enforcing consistency between the distribution’s zeroth moment derived from both the Smoluchowski equation and the scaling distribution ansatz, we find values for the scaling exponents w and z in terms of the scaling exponent τ and the kernel homogeneity λ which are not equivalent to their asymptotic, scaling forms. The predicted values do agree well, however, with intermediate time values found in simulations by Kang, Redner, Meakin, and Leyvraz [Phys Rev. A 33, 1171 (1986)]. By enforcing consistency between all moment orders, the asymptotic exponent values are found. These results imply the lowest-order moments approach their scaling values quickest
Elliptic flow of resonances at RHIC: probing final state interactions and the structure of resonances
We propose the measurement of the elliptic flow of hadron resonances at the
Relativistic Heavy Ion Collider as a tool to probe the amount of hadronic final
state interactions for resonances at intermediate and large transverse momenta.
This can be achieved by looking at systematic deviations of the measured flow
coefficient from the scaling law given by the quark recombination
formalism. Our method can be generalized to explore the structure of exotic
particles, such as the recently found pentaquark .Comment: 5 pages, 2 figures; v2: accepted version for publication in Physical
Review C rapid communication
Gelation in Aerosols; Non-Mean-Field Aggregation and Kinetics
Nature has many examples of systems of particles suspended in a fluid phase; colloids when in a liquid, aerosols when in a gas. These systems are inherently unstable since if the particles can come together, van der Waals forces will keep them together. In this work we studied the aggregation kinetics of particulate systems, most often aerosols. The emphasis of our work was to study dense systems and systems that gel since previous work had not considered these. Our work obtained a number of significant discoveries and results which are reported here
Evidence from Identified Particles for Active Quark and Gluon Degrees of Freedom
Measurements of intermediate pT (1.5 < pT < 5.0 GeV/c) identified particle
distributions in heavy ion collisions at SPS and RHIC energies display striking
dependencies on the number of constituent quarks in the corresponding hadron.
One finds that elliptic flow at intermediate pT follows a constituent quark
scaling law as predicted by models of hadron formation through coalescence. In
addition, baryon production is also found to increase with event multiplicity
much faster than meson production. The rate of increase is similar for all
baryons, and seemingly independent of mass. This indicates that the number of
constituent quarks determines the multiplicity dependence of identified hadron
production at intermediate pT. We review these measurements and interpret the
experimental findings.Comment: 8 pages, 5 figures, proceedings for SQM2006 conference in Los Angele
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