146 research outputs found

    Comments on Noncommutative ADHM Construction

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    We extend the method of matrix partition to obtain explicitly the gauge field for noncommutative ADHM construction in some general cases. As an application of this method we apply it to the U(2) 2-instanton and get explicit result for the gauge fields in the coincident instanton limit. We also easily apply it to the noncommutative 't Hooft instantons in the appendix.Comment: 17 pages, LaTeX; an appendix added, typos corrected, refs adde

    A note on instanton counting for N=2 gauge theories with classical gauge groups

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    We study the prepotential of N=2 gauge theories using the instanton counting techniques introduced by Nekrasov. For the SO theories without matter we find a closed expression for the full prepotential and its string theory gravitational corrections. For the more subtle case of Sp theories without matter we discuss general features and compute the prepotential up to instanton number three. We also briefly discuss SU theories with matter in the symmetric and antisymmetric representations. We check all our results against the predictions of the corresponding Seiberg-Witten geometries.Comment: 24 pages, LaTeX. v2: refs added. v3: typos correcte

    The Infrared Behaviour of the Pure Yang-Mills Green Functions

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    We review the infrared properties of the pure Yang-Mills correlators and discuss recent results concerning the two classes of low-momentum solutions for them reported in literature; i.e. decoupling and scaling solutions. We will mainly focuss on the Landau gauge and pay special attention to the results inferred from the analysis of the Dyson-Schwinger equations of the theory and from "{\it quenched}" lattice QCD. The results obtained from properly interplaying both approaches are strongly emphasized.Comment: Final version to be published in FBS (54 pgs., 11 figs., 4 tabs

    Propagators in Noncommutative Instantons

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    We explicitly construct Green functions for a field in an arbitrary representation of gauge group propagating in noncommutative instanton backgrounds based on the ADHM construction. The propagators for spinor and vector fields can be constructed in terms of those for the scalar field in noncommutative instanton background. We show that the propagators in the adjoint representation are deformed by noncommutativity while those in the fundamental representation have exactly the same form as the commutative case.Comment: 28 pages, Latex, v2: A few typos correcte

    Formation of dense partonic matter in relativistic nucleus-nucleus collisions at RHIC: Experimental evaluation by the PHENIX collaboration

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    Extensive experimental data from high-energy nucleus-nucleus collisions were recorded using the PHENIX detector at the Relativistic Heavy Ion Collider (RHIC). The comprehensive set of measurements from the first three years of RHIC operation includes charged particle multiplicities, transverse energy, yield ratios and spectra of identified hadrons in a wide range of transverse momenta (p_T), elliptic flow, two-particle correlations, non-statistical fluctuations, and suppression of particle production at high p_T. The results are examined with an emphasis on implications for the formation of a new state of dense matter. We find that the state of matter created at RHIC cannot be described in terms of ordinary color neutral hadrons.Comment: 510 authors, 127 pages text, 56 figures, 1 tables, LaTeX. Submitted to Nuclear Physics A as a regular article; v3 has minor changes in response to referee comments. Plain text data tables for the points plotted in figures for this and previous PHENIX publications are (or will be) publicly available at http://www.phenix.bnl.gov/papers.htm

    Zero Modes and the Atiyah-Singer Index in Noncommutative Instantons

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    We study the bosonic and fermionic zero modes in noncommutative instanton backgrounds based on the ADHM construction. In k instanton background in U(N) gauge theory, we show how to explicitly construct 4Nk (2Nk) bosonic (fermionic) zero modes in the adjoint representation and 2k (k) bosonic (fermionic) zero modes in the fundamental representation from the ADHM construction. The number of fermionic zero modes is also shown to be exactly equal to the Atiyah-Singer index of the Dirac operator in the noncommutative instanton background. We point out that (super)conformal zero modes in non-BPS instantons are affected by the noncommutativity. The role of Lorentz symmetry breaking by the noncommutativity is also briefly discussed to figure out the structure of U(1) instantons.Comment: v3: 24 pages, Latex, corrected typos, references added, to appear in Phys. Rev.

    Measurement of the CP-Violating Asymmetry Amplitude sin2β\beta

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    We present results on time-dependent CP-violating asymmetries in neutral B decays to several CP eigenstates. The measurements use a data sample of about 88 million Y(4S) --> B Bbar decays collected between 1999 and 2002 with the BABAR detector at the PEP-II asymmetric-energy B Factory at SLAC. We study events in which one neutral B meson is fully reconstructed in a final state containing a charmonium meson and the other B meson is determined to be either a B0 or B0bar from its decay products. The amplitude of the CP-violating asymmetry, which in the Standard Model is proportional to sin2beta, is derived from the decay-time distributions in such events. We measure sin2beta = 0.741 +/- 0.067 (stat) +/- 0.033 (syst) and |lambda| = 0.948 +/- 0.051 (stat) +/- 0.017 (syst). The magnitude of lambda is consistent with unity, in agreement with the Standard Model expectation of no direct CP violation in these modes

    Rationale and design of 'discontinuing statins in multimorbid older adults without cardiovascular disease (STREAM)': study protocol of a randomised non-inferiority clinical trial.

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    Statins are among the most widely used drugs. While they are effective for primary and secondary prevention of cardiovascular (CV) disease in middle-aged subjects, their benefits for prevention in older adults (aged ≥70 years) without CV disease are uncertain, particularly for those with multimorbidity. Statin side effects and drug interactions are common in older patients and may negatively impact quality of life. To date, the only randomised controlled trial (RCT) investigating statin discontinuation in older adults has demonstrated no difference in survival but did note a small improvement in quality of life for those who discontinued statins. However, this trial exclusively enrolled patients with a life expectancy <1 year. Therefore, the present RCT aims to assess the safety and potential benefits of statin discontinuation in primary prevention for the ever-growing population of multimorbid older adults. This study is a multicentre, randomised, non-inferiority trial conducted in both inpatient and outpatient settings in Switzerland, France and the Netherlands, targeting patients using statins for primary prevention. 1800 participants are randomly assigned 1:1 to either discontinue (intervention arm) or continue (control arm) statin therapy. The primary objective is to compare the primary composite endpoint of major CV events (non-fatal myocardial infarction or non-fatal ischaemic stroke) and all-cause death between the control and intervention groups over a follow-up duration of up to 48 months. We hypothesise that discontinuing statins does not result in shorter event-free survival, with a non-inferiority margin set at 5.2 weeks over a 2-year observation period. Secondary objectives are to compare patient-centred outcomes (health-related quality of life, muscle pain symptoms, falls and sarcopenia) and all-cause death, non-CV death, major CV events and coronary and peripheral artery revascularisation. The study is open-labelled, with blinded outcome adjudication of the primary endpoints. The trial protocol has received approval from the local ethics committees in Switzerland, France and the Netherlands. Results will be published in a peer-reviewed journal. Clinicaltrials.gov: NCT05178420; BASEC (Swiss Ethics Commission): 2021-01513; FOPH (Swiss national portal): SNCTP000005172; Netherlands Trial Register: NL83907.058.23; France Trial Register: 22.04747.000158- IDRCB 2022-A02481-42

    The Physics of the B Factories

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