29,502 research outputs found
On the semantics of fair parallelism
Suppose that a programming language involves, among other familiar ways of composing commands Ci, a "parallel" construct (C1 par C2) .
One expects, when using this language, that a sequence such as
x := O; y := 1; (x := 1 par (while x=0 do y := y+1)) should be guaranteed to terminate in whatever context it is executed
Metro Raise: Boosting the Earned Income Tax Credit to Help Metropolitan Workers and Families
Argues for increasing the Earned Income Tax Credit and expanding its options in order to help low-income workers and families meet rising costs and to ensure more inclusive economic growth. Estimates the impact of various proposals on metropolitan areas
Tall sections from non-minimal transformations
In previous work, we have shown that elliptic fibrations with two sections,
or Mordell-Weil rank one, can always be mapped birationally to a Weierstrass
model of a certain form, namely, the Jacobian of a model.
Most constructions of elliptically fibered Calabi-Yau manifolds with two
sections have been carried out assuming that the image of this birational map
was a "minimal" Weierstrass model. In this paper, we show that for some
elliptically fibered Calabi-Yau manifolds with Mordell-Weil rank-one, the
Jacobian of the model is not minimal. Said another way,
starting from a Calabi-Yau Weierstrass model, the total space must be blown up
(thereby destroying the "Calabi-Yau" property) in order to embed the model into
. In particular, we show that the elliptic fibrations studied
recently by Klevers and Taylor fall into this class of models.Comment: 16 page
Recent Immigration to Philadelphia: Regional Change in a Re-Emerging Gateway
Analyzes 1970-2006 trends in the growth and characteristics of the city's immigrant population. Presents data by regional origin, settlement area, arrival year, citizenship status, age, gender, education, and language, and in comparison with other cities
Revealing Compressed Stops Using High-Momentum Recoils
Searches for supersymmetric top quarks at the LHC have been making great
progress in pushing sensitivity out to higher mass, but are famously plagued by
gaps in coverage around lower-mass regions where the decay phase space is
closing off. Within the common stop-NLSP / neutralino-LSP simplified model, the
line in the mass plane where there is just enough phase space to produce an
on-shell top quark remains almost completely unconstrained. Here, we show that
is possible to define searches capable of probing a large patch of this
difficult region, with S/B ~ 1 and significances often well beyond 5 sigma. The
basic strategy is to leverage the large energy gain of LHC Run 2, leading to a
sizable population of stop pair events recoiling against a hard jet. The recoil
not only re-establishes a MET signature, but also leads to a distinctive
anti-correlation between the MET and the recoil jet transverse vectors when the
stops decay all-hadronically. Accounting for jet combinatorics, backgrounds,
and imperfections in MET measurements, we estimate that Run 2 will already
start to close the gap in exclusion sensitivity with the first few 10s of
inverse-fb. By 300/fb, exclusion sensitivity may extend from stop masses of 550
GeV on the high side down to below 200 GeV on the low side, approaching the
"stealth" point at m(stop) = m(top) and potentially overlapping with limits
from top pair cross section and spin correlation measurements.Comment: 17 pages, 6 figure
Highly Deformable Graphene Kirigami
Graphene's exceptional mechanical properties, including its highest-known
stiffness (1 TPa) and strength (100 GPa) have been exploited for various
structural applications. However, graphene is also known to be quite brittle,
with experimentally-measured tensile fracture strains that do not exceed a few
percent. In this work, we introduce the notion of graphene kirigami, where
concepts that have been used almost exclusively for macroscale structures are
applied to dramatically enhance the stretchability of both zigzag and armchair
graphene. Specifically, we show using classical molecular dynamics simulations
that the yield and fracture strains of graphene can be enhanced by about a
factor of three using kirigami as compared to standard monolayer graphene. This
enhanced ductility in graphene should open up interesting opportunities not
only mechanically, but also in coupling to graphene's electronic behavior.Comment: 5 pages, 7 figure
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