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Trends in life cycle greenhouse gas emissions of future light duty electric vehicles
The majority of previous studies examining life cycle greenhouse gas (LCGHG) emissions of battery electric vehicles (BEVs) have focused on efficiency-oriented vehicle designs with limited battery capacities. However, two dominant trends in the US BEV market make these studies increasingly obsolete: sales show significant increases in battery capacity and attendant range and are increasingly dominated by large luxury or high-performance vehicles. In addition, an era of new use and ownership models may mean significant changes to vehicle utilization, and the carbon intensity of electricity is expected to decrease. Thus, the question is whether these trends significantly alter our expectations of future BEV LCGHG emissions. To answer this question, three archetypal vehicle designs for the year 2025 along with scenarios for increased range and different use models are simulated in an LCGHG model: an efficiency-oriented compact vehicle; a high performance luxury sedan; and a luxury sport utility vehicle. While production emissions are less than 10% of LCGHG emissions for today's gasoline vehicles, they account for about 40% for a BEV, and as much as two-thirds of a future BEV operated on a primarily renewable grid. Larger battery systems and low utilization do not outweigh expected reductions in emissions from electricity used for vehicle charging. These trends could be exacerbated by increasing BEV market shares for larger vehicles. However, larger battery systems could reduce per-mile emissions of BEVs in high mileage applications, like on-demand ride sharing or shared vehicle fleets, meaning that trends in use patterns may countervail those in BEV design
Integral Grothendieck-Riemann-Roch theorem
We show that, in characteristic zero, the obvious integral version of the
Grothendieck-Riemann-Roch formula obtained by clearing the denominators of the
Todd and Chern characters is true (without having to divide the Chow groups by
their torsion subgroups). The proof introduces an alternative to Grothendieck's
strategy: we use resolution of singularities and the weak factorization theorem
for birational maps.Comment: 24 page
Classification of double flag varieties of complexity 0 and 1
A classification of double flag varieties of complexity 0 and 1 is obtained.
An application of this problem to decomposing tensor products of irreducible
representations of semisimple Lie groups is considered
The three-quark static potential in perturbation theory
We study the three-quark static potential in perturbation theory in QCD. A
complete next-to-leading order calculation is performed in the singlet, octets
and decuplet channels and the potential exponentiation is demonstrated. The
mixing of the octet representations is calculated. At next-to-next-to-leading
order, the subset of diagrams producing three-body forces is identified in
Coulomb gauge and its contribution to the potential calculated. Combining it
with the contribution of the two-body forces, which may be extracted from the
quark-antiquark static potential, we obtain the complete
next-to-next-to-leading order three-quark static potential in the
colour-singlet channel.Comment: 36 pages, 11 figures, version published in Phys.Rev.
Remarks on the structure constants of the Verlinde algebra associated to
The structure constants of the Verlinde
algebra as functions of either vanish or can be expressed after a change
of variable as the weight function of an irreducible representation of .
We give a similar formula in the case.Comment: 5 pages, AmsTeX, 1 figure available on reques
Degree formula for connective K-theory
We apply the degree formula for connective -theory to study rational
contractions of algebraic varieties. Examples include rationally connected
varieties and complete intersections.Comment: 14 page
An Excess of Jupiter Analogs in Super-Earth Systems
We use radial velocity observations to search for long-period gas giant
companions in systems hosting inner super-Earth (1-4 R_Earth, 1-10 M_Earth)
planets to constrain formation and migration scenarios for this population. We
consistently re-fit published RV datasets for 65 stars and find 9 systems with
statistically significant trends indicating the presence of an outer companion.
We combine these RV data with AO images to constrain the masses and semi-major
axes of these companions. We quantify our sensitivity to the presence of
long-period companions by fitting the sample with a power law distribution and
find an occurrence rate of 39+/-7% for companions 0.5-20 M_Jup and 1-20 AU.
Half of our systems were discovered by the transit method and half were
discovered by the RV method. While differences in RV baselines and number of
data points between the two samples lead to different sensitivities to distant
companions, we find that occurrence rates of gas giant companions in each
sample are consistent at the 0.5 level. We compare the frequency of
Jupiter analogs in these systems to the equivalent rate from field star surveys
and find that Jupiter analogs are more common around stars hosting
super-Earths. We conclude that the presence of outer gas giants does not
suppress the formation of inner super-Earths, and that these two populations of
planets instead appear to be correlated. We also find that the stellar
metallicities of systems with gas giant companions are higher than those
without companions, in agreement with the well-established metallicity
correlation from RV surveys of field stars.Comment: published in A
Stringy K-theory and the Chern character
For a finite group G acting on a smooth projective variety X, we construct
two new G-equivariant rings: first the stringy K-theory of X, and second the
stringy cohomology of X. For a smooth Deligne-Mumford stack Y we also construct
a new ring called the full orbifold K-theory of Y. For a global quotient
Y=[X/G], the ring of G-invariants of the stringy K-theory of X is a subalgebra
of the full orbifold K-theory of the the stack Y and is linearly isomorphic to
the ``orbifold K-theory'' of Adem-Ruan (and hence Atiyah-Segal), but carries a
different, ``quantum,'' product, which respects the natural group grading. We
prove there is a ring isomorphism, the stringy Chern character, from stringy
K-theory to stringy cohomology, and a ring homomorphism from full orbifold
K-theory to Chen-Ruan orbifold cohomology. These Chern characters satisfy
Grothendieck-Riemann-Roch for etale maps.
We prove that stringy cohomology is isomorphic to Fantechi and Goettsche's
construction. Since our constructions do not use complex curves, stable maps,
admissible covers, or moduli spaces, our results simplify the definitions of
Fantechi-Goettsche's ring, of Chen-Ruan's orbifold cohomology, and of
Abramovich-Graber-Vistoli's orbifold Chow.
We conclude by showing that a K-theoretic version of Ruan's Hyper-Kaehler
Resolution Conjecture holds for symmetric products.
Our results hold both in the algebro-geometric category and in the
topological category for equivariant almost complex manifolds.Comment: Exposition improved and additional details provided. To appear in
Inventiones Mathematica
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