25,354 research outputs found
Localized mirror functor for Lagrangian immersions, and homological mirror symmetry for P 1 a,b,c
This paper gives a new way of constructing Landau–Ginzburg mirrors usingdeformation theory of Lagrangian immersions motivated by the works of Seidel,Strominger –Yau–Zaslow and Fukaya–Oh–Ohta–Ono. Moreover, we construct acanonical functor from the Fukaya category to the mirror category of matrixfactorizations. This functor derives homological mirror symmetry under someexplicit assumptions.As an application, the construction is applied to spheres with three orbifoldpoints to produce their quantum-corrected mirrors and derive homological mirrorsymmetry. Furthermore, we discover an enumerative meaning of the (inverse)mirror map for elliptic curve quotients
Radioactive silicon as a marker in thin-film silicide formation
A new technique using radioactive 31Si (half-life =2.62 h), formed in a nuclear reactor, as a marker for studying silicide formation is described. A few hundred angstroms of radioactive silicon is first deposited onto the silicon substrate, followed immediately by the deposition of a few thousand angstroms of the metal. When the sample is heated, a silicide is first formed with the radioactive silicon. Upon further silicide formation, this band of radioactive silicide can move to the surface of the sample if silicide formation takes place by diffusion of the metal or by silicon substitutional and/or vacancy diffusion. However, if the band of radioactive silicide stays at the silicon substrate interface it can be concluded that silicon diffuses by interstitial and/or grain-boundary diffusion. This technique was tested by studying the formation of Ni2Si on silicon at 330 °C. From a combination of ion-beam sputtering, radioactivity measurement, and Rutherford backscattering it is found that the band of radioactive silicide moves to the surface of the sample during silicide formation. From these results, implanted noble-gas marker studies and the rate dependence of Ni2Si growth on grain size, it is concluded that nickel is the dominant diffusing species during Ni2Si formation, and that it moves by grain-boundary diffusion
New variables, the gravitational action, and boosted quasilocal stress-energy-momentum
This paper presents a complete set of quasilocal densities which describe the
stress-energy-momentum content of the gravitational field and which are built
with Ashtekar variables. The densities are defined on a two-surface which
bounds a generic spacelike hypersurface of spacetime. The method used
to derive the set of quasilocal densities is a Hamilton-Jacobi analysis of a
suitable covariant action principle for the Ashtekar variables. As such, the
theory presented here is an Ashtekar-variable reformulation of the metric
theory of quasilocal stress-energy-momentum originally due to Brown and York.
This work also investigates how the quasilocal densities behave under
generalized boosts, i. e. switches of the slice spanning . It is
shown that under such boosts the densities behave in a manner which is similar
to the simple boost law for energy-momentum four-vectors in special relativity.
The developed formalism is used to obtain a collection of two-surface or boost
invariants. With these invariants, one may ``build" several different mass
definitions in general relativity, such as the Hawking expression. Also
discussed in detail in this paper is the canonical action principle as applied
to bounded spacetime regions with ``sharp corners."Comment: Revtex, 41 Pages, 4 figures added. Final version has been revised and
improved quite a bit. To appear in Classical and Quantum Gravit
Epitaxial growth of deposited amorphous layer by laser annealing
We demonstrate that a single short pulse of laser irradiation of appropriate energy is capable of recrystallizing in open air an amorphous Si layer deposited on a (100) single-crystal substrate into an epitaxial layer. The laser pulse annealing technique is shown to overcome the interfacial oxide obstacle which usually leads to polycrystalline formation in normal thermal annealing
Hamiltonians for a general dilaton gravity theory on a spacetime with a non-orthogonal, timelike or spacelike outer boundary
A generalization of two recently proposed general relativity Hamiltonians, to
the case of a general (d+1)-dimensional dilaton gravity theory in a manifold
with a timelike or spacelike outer boundary, is presented.Comment: 17 pages, 3 figures. Typos correcte
Evolution and CNO yields of Z=10^-5 stars and possible effects on CEMP production
Our main goals are to get a deeper insight into the evolution and final fates
of intermediate-mass, extremely metal-poor (EMP) stars. We also aim to
investigate their C, N, and O yields. Using the Monash University Stellar
Evolution code we computed and analysed the evolution of stars of metallicity Z
= 10^-5 and masses between 4 and 9 M_sun, from their main sequence until the
late thermally pulsing (super) asymptotic giant branch, TP-(S)AGB phase. Our
model stars experience a strong C, N, and O envelope enrichment either due to
the second dredge-up, the dredge-out phenomenon, or the third dredge-up early
during the TP-(S)AGB phase. Their late evolution is therefore similar to that
of higher metallicity objects. When using a standard prescription for the mass
loss rates during the TP-(S)AGB phase, the computed stars lose most of their
envelopes before their cores reach the Chandrasekhar mass, so our standard
models do not predict the occurrence of SNI1/2 for Z = 10^-5 stars. However, we
find that the reduction of only one order of magnitude in the mass-loss rates,
which are particularly uncertain at this metallicity, would prevent the
complete ejection of the envelope, allowing the stars to either explode as an
SNI1/2 or become an electron-capture SN. Our calculations stop due to an
instability near the base of the convective envelope that hampers further
convergence and leaves remnant envelope masses between 0.25 M_sun for our 4
M_sun model and 1.5 M_sun for our 9 M_sun model. We present two sets of C, N,
and O yields derived from our full calculations and computed under two
different assumptions, namely, that the instability causes a practically
instant loss of the remnant envelope or that the stars recover and proceed with
further thermal pulses. Our results have implications for the early chemical
evolution of the Universe.Comment: 12 pages, 13 figures, accepted for publication in A&
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