9 research outputs found
Chiral-Yang-Mills theory, non commutative differential geometry, and the need for a Lie super-algebra
In Yang-Mills theory, the charges of the left and right massless Fermions are
independent of each other. We propose a new paradigm where we remove this
freedom and densify the algebraic structure of Yang-Mills theory by integrating
the scalar Higgs field into a new gauge-chiral 1-form which connects Fermions
of opposite chiralities. Using the Bianchi identity, we prove that the
corresponding covariant differential is associative if and only if we gauge a
Lie-Kac super-algebra. In this model, spontaneous symmetry breakdown naturally
occurs along an odd generator of the super-algebra and induces a representation
of the Connes-Lott non commutative differential geometry of the 2-point finite
space.Comment: 17 pages, no figur
Wess-Zumino model with exact supersymmetry on the lattice
A lattice formulation of the four dimensional Wess-Zumino model that uses
Ginsparg-Wilson fermions and keeps exact supersymmetry is presented. The
supersymmetry transformation that leaves invariant the action at finite lattice
spacing is determined by performing an iterative procedure in the coupling
constant. The closure of the algebra, generated by this transformation is also
showed.Comment: 13 pages. Few references added. New appendix on Ward identity added.
Version to be published in JHE
Classical symmetric functions in superspace
We present the basic elements of a generalization of symmetric function
theory involving functions of commuting and anticommuting (Grassmannian)
variables. These new functions, called symmetric functions in superspace, are
invariant under the diagonal action of the symmetric group on the sets of
commuting and anticommuting variables. In this work, we present the superspace
extension of the classical bases, namely, the monomial symmetric functions, the
elementary symmetric functions, the completely symmetric functions, and the
power sums. Various basic results, such as the generating functions for the
multiplicative bases, Cauchy formulas, involution operations as well as the
combinatorial scalar product are also generalized.Comment: 21 pages, this supersedes the first part of math.CO/041230
Supersymmetry on a Spatial Lattice
We construct a variety of supersymmetric gauge theories on a spatial lattice,
including N=4 supersymmetric Yang-Mills theory in 3+1 dimensions. Exact lattice
supersymmetry greatly reduces or eliminates the need for fine tuning to arrive
at the desired continuum limit in these examples.Comment: Version 3: Text brought in line with published version (extended
discussion of orbifolding
Lattice supersymmetry, superfields and renormalization
We study Euclidean lattice formulations of non-gauge supersymmetric models
with up to four supercharges in various dimensions. We formulate the conditions
under which the interacting lattice theory can exactly preserve one or more
nilpotent anticommuting supersymmetries. We introduce a superfield formalism,
which allows the enumeration of all possible lattice supersymmetry invariants.
We use it to discuss the formulation of Q-exact lattice actions and their
renormalization in a general manner. In some examples, one exact supersymmetry
guarantees finiteness of the continuum limit of the lattice theory. As a
consequence, we show that the desired quantum continuum limit is obtained
without fine tuning for these models. Finally, we discuss the implications and
possible further applications of our results to the study of gauge and
non-gauge models.Comment: 44 pages, 1 figur
Spin chains with dynamical lattice supersymmetry
Spin chains with exact supersymmetry on finite one-dimensional lattices are
considered. The supercharges are nilpotent operators on the lattice of
dynamical nature: they change the number of sites. A local criterion for the
nilpotency on periodic lattices is formulated. Any of its solutions leads to a
supersymmetric spin chain. It is shown that a class of special solutions at
arbitrary spin gives the lattice equivalents of the N=(2,2) superconformal
minimal models. The case of spin one is investigated in detail: in particular,
it is shown that the Fateev-Zamolodchikov chain and its off-critical extension
admits a lattice supersymmetry for all its coupling constants. Its
supersymmetry singlets are thoroughly analysed, and a relation between their
components and the weighted enumeration of alternating sign matrices is
conjectured.Comment: Revised version, 52 pages, 2 figure
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Impact of COVID-19 on Cardiovascular Testing in the United States Versus the Rest of the World
Objectives: This study sought to quantify and compare the decline in volumes of cardiovascular procedures between the United States and non-U.S. institutions during the early phase of the coronavirus disease-2019 (COVID-19) pandemic. Background: The COVID-19 pandemic has disrupted the care of many non-COVID-19 illnesses. Reductions in diagnostic cardiovascular testing around the world have led to concerns over the implications of reduced testing for cardiovascular disease (CVD) morbidity and mortality. Methods: Data were submitted to the INCAPS-COVID (International Atomic Energy Agency Non-Invasive Cardiology Protocols Study of COVID-19), a multinational registry comprising 909 institutions in 108 countries (including 155 facilities in 40 U.S. states), assessing the impact of the COVID-19 pandemic on volumes of diagnostic cardiovascular procedures. Data were obtained for April 2020 and compared with volumes of baseline procedures from March 2019. We compared laboratory characteristics, practices, and procedure volumes between U.S. and non-U.S. facilities and between U.S. geographic regions and identified factors associated with volume reduction in the United States. Results: Reductions in the volumes of procedures in the United States were similar to those in non-U.S. facilities (68% vs. 63%, respectively; p = 0.237), although U.S. facilities reported greater reductions in invasive coronary angiography (69% vs. 53%, respectively; p < 0.001). Significantly more U.S. facilities reported increased use of telehealth and patient screening measures than non-U.S. facilities, such as temperature checks, symptom screenings, and COVID-19 testing. Reductions in volumes of procedures differed between U.S. regions, with larger declines observed in the Northeast (76%) and Midwest (74%) than in the South (62%) and West (44%). Prevalence of COVID-19, staff redeployments, outpatient centers, and urban centers were associated with greater reductions in volume in U.S. facilities in a multivariable analysis. Conclusions: We observed marked reductions in U.S. cardiovascular testing in the early phase of the pandemic and significant variability between U.S. regions. The association between reductions of volumes and COVID-19 prevalence in the United States highlighted the need for proactive efforts to maintain access to cardiovascular testing in areas most affected by outbreaks of COVID-19 infection