2,070 research outputs found
New Methods for Characterizing Phases of 2D Supersymmetric Gauge Theories
We study the physics of two-dimensional N=(2,2) gauged linear sigma models
(GLSMs) via the two-sphere partition function. We show that the classical phase
boundaries separating distinct GLSM phases, which are described by the
secondary fan construction for abelian GLSMs, are completely encoded in the
analytic structure of the partition function. The partition function of a
non-abelian GLSM can be obtained as a limit from an abelian theory; we utilize
this fact to show that the phases of non-abelian GLSMs can be obtained from the
secondary fan of the associated abelian GLSM. We prove that the partition
function of any abelian GLSM satisfies a set of linear differential equations;
these reduce to the familiar A-hypergeometric system of Gel'fand, Kapranov, and
Zelevinski for GLSMs describing complete intersections in toric varieties. We
develop a set of conditions that are necessary for a GLSM phase to admit an
interpretation as the low-energy limit of a non-linear sigma model with a
Calabi-Yau threefold target space. Through the application of these criteria we
discover a class of GLSMs with novel geometric phases corresponding to
Calabi-Yau manifolds that are branched double-covers of Fano threefolds. These
criteria provide a promising approach for constructing new Calabi-Yau
geometries.Comment: 25 pages + references, appendices. v2: references added, typos
corrected. v3: two small typos correcte
The Landscape of M-theory Compactifications on Seven-Manifolds with Holonomy
We study the physics of globally consistent four-dimensional
supersymmetric M-theory compactifications on manifolds constructed via
twisted connected sum; there are now perhaps fifty million examples of these
manifolds. We study a rich example that exhibits gauge symmetry and a
spectrum of massive charged particles that includes a trifundamental. Applying
recent mathematical results to this example, we compute membrane instanton
corrections to the superpotential and spacetime topology change in a compact
model; the latter include both the (non-isolated) flop and conifold
transitions. The conifold transition spontaneously breaks the gauge symmetry to
, and associated field theoretic computations of particle charges make
correct predictions for the topology of the deformed manifold. We discuss
physical aspects of the abelian landscape broadly, including aspects of
Higgs and Coulomb branches, membrane instanton corrections, and some general
aspects of topology change.Comment: v1: 37 pages. v2: references added. v3: more discussion of instanton
zero modes. JHEP version v4: references correcte
How Leaders Invest Staffing Resources for Learning Improvement
Analyzes staffing challenges that guide school leaders' resource decisions in the context of a learning improvement agenda, staff resource investment strategies that improve learning outcomes equitably, and ways to win support for differential investment
Generic construction of the Standard Model gauge group and matter representations in F-theory
We describe general classes of 6D and 4D F-theory models with gauge group
. We prove that this set of constructions gives all possible
consistent 6D supergravity theories with no tensor multiplets having this gauge
group and the corresponding generic matter representations, which include those
of the MSSM. We expect, though do not prove, that these models are similarly
generic for 6D theories with tensor multiplets and for 4D
supergravity theories. The largest class of these constructions comes from
deforming an underlying geometry with gauge symmetry .Comment: 10 pages, LaTeX; references added, minor edit
An Experiment In Collaborative Spreadsheet Development
To study the extent to which group development can reduce spreadsheet errors, an experiment compared error rates in spreadsheet development by subjects working alone (monads) and by subjects working in groups of three (triads). Impressively, triads made 78% fewer errors than monads. However, this was not as large a reduction as nominal group analysis suggests was possible. Members of triads were satisfied with group development. However, triads whose work went most smoothly, whose members were most satisfied with group interactions, and that had the loosest leadership structure were significantly more likely to make errors than other triads
Can modified gravity explain accelerated cosmic expansion?
We show that the recently suggested explanations of cosmic acceleration by
the modification of gravity at small curvature suffer violent instabilities and
strongly disagree with the known properties of gravitational interactions.Comment: 4 pages, no figure, revised version (one footnote added
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