2,270 research outputs found
The Quantum McKay Correspondence for polyhedral singularities
Let G be a polyhedral group, namely a finite subgroup of SO(3). Nakamura's
G-Hilbert scheme provides a preferred Calabi-Yau resolution Y of the polyhedral
singularity C^3/G. The classical McKay correspondence describes the classical
geometry of Y in terms of the representation theory of G. In this paper we
describe the quantum geometry of Y in terms of R, an ADE root system associated
to G. Namely, we give an explicit formula for the Gromov-Witten partition
function of Y as a product over the positive roots of R. In terms of counts of
BPS states (Gopakumar-Vafa invariants), our result can be stated as a
correspondence: each positive root of R corresponds to one half of a genus zero
BPS state. As an application, we use the crepant resolution conjecture to
provide a full prediction for the orbifold Gromov-Witten invariants of [C^3/G].Comment: Introduction rewritten. Issue regarding non-uniqueness of conifold
resolution clarified. Version to appear in Inventione
Curve counting via stable pairs in the derived category
For a nonsingular projective 3-fold , we define integer invariants
virtually enumerating pairs where is an embedded curve and
is a divisor. A virtual class is constructed on the associated
moduli space by viewing a pair as an object in the derived category of . The
resulting invariants are conjecturally equivalent, after universal
transformations, to both the Gromov-Witten and DT theories of . For
Calabi-Yau 3-folds, the latter equivalence should be viewed as a wall-crossing
formula in the derived category.
Several calculations of the new invariants are carried out. In the Fano case,
the local contributions of nonsingular embedded curves are found. In the local
toric Calabi-Yau case, a completely new form of the topological vertex is
described.
The virtual enumeration of pairs is closely related to the geometry
underlying the BPS state counts of Gopakumar and Vafa. We prove that our
integrality predictions for Gromov-Witten invariants agree with the BPS
integrality. Conversely, the BPS geometry imposes strong conditions on the
enumeration of pairs.Comment: Corrected typos and duality error in Proposition 4.6. 47 page
Holomorphic anomaly equations and the Igusa cusp form conjecture
Let be a K3 surface and let be an elliptic curve. We solve the
reduced Gromov-Witten theory of the Calabi-Yau threefold for all
curve classes which are primitive in the K3 factor. In particular, we deduce
the Igusa cusp form conjecture.
The proof relies on new results in the Gromov-Witten theory of elliptic
curves and K3 surfaces. We show the generating series of Gromov-Witten classes
of an elliptic curve are cycle-valued quasimodular forms and satisfy a
holomorphic anomaly equation. The quasimodularity generalizes a result by
Okounkov and Pandharipande, and the holomorphic anomaly equation proves a
conjecture of Milanov, Ruan and Shen. We further conjecture quasimodularity and
holomorphic anomaly equations for the cycle-valued Gromov-Witten theory of
every elliptic fibration with section. The conjecture generalizes the
holomorphic anomaly equations for ellliptic Calabi-Yau threefolds predicted by
Bershadsky, Cecotti, Ooguri, and Vafa. We show a modified conjecture holds
numerically for the reduced Gromov-Witten theory of K3 surfaces in primitive
classes.Comment: 68 page
FiND: Few-shot three-dimensional image-free confocal focusing on point-like emitters
Confocal fluorescence microscopy is widely applied for the study of
point-like emitters such as biomolecules, material defects, and quantum light
sources. Confocal techniques offer increased optical resolution, dramatic
fluorescence background rejection and sub-nanometer localization, useful in
super-resolution imaging of fluorescent biomarkers, single-molecule tracking,
or the characterization of quantum emitters. However, rapid, noise-robust
automated 3D focusing on point-like emitters has been missing for confocal
microscopes. Here, we introduce FiND (Focusing in Noisy Domain), an
imaging-free, non-trained 3D focusing framework that requires no hardware
add-ons or modifications. FiND achieves focusing for signal-to-noise ratios
down to 1, with a few-shot operation for signal-to-noise ratios above 5. FiND
enables unsupervised, large-scale focusing on a heterogeneous set of quantum
emitters. Additionally, we demonstrate the potential of FiND for real-time 3D
tracking by following the drift trajectory of a single NV center indefinitely
with a positional precision of < 10 nm. Our results show that FiND is a useful
focusing framework for the scalable analysis of point-like emitters in biology,
material science, and quantum optics.Comment: 17 pages, 7 figure
Strengthening the Cohomological Crepant Resolution Conjecture for Hilbert-Chow morphisms
Given any smooth toric surface S, we prove a SYM-HILB correspondence which
relates the 3-point, degree zero, extended Gromov-Witten invariants of the
n-fold symmetric product stack [Sym^n(S)] of S to the 3-point extremal
Gromov-Witten invariants of the Hilbert scheme Hilb^n(S) of n points on S. As
we do not specialize the values of the quantum parameters involved, this result
proves a strengthening of Ruan's Cohomological Crepant Resolution Conjecture
for the Hilbert-Chow morphism from Hilb^n(S) to Sym^n(S) and yields a method of
reconstructing the cup product for Hilb^n(S) from the orbifold invariants of
[Sym^n(S)].Comment: Revised versio
Bis-spirolabdane Diterpenoids from Leonotis nepetaefolia
Ten new bis-spirolabdane diterpenoids, leonepetaefolins A–E (1, 3, 5, 7, 9) and 15-epi-leonepetaefolins A-E (2, 4, 6, 8, 10), together with eight known labdane diterpenoids (11–18) as well as two known flavonoids apigenin and cirsiliol, were isolated from the leaves of Leonotis nepetaefolia. The structures of the new compounds were determined on the basis of 1D-and 2D-NMR experiments including 1H, 13C, DEPT, 1H-1H COSY, HSQC, HMBC, and NOESY. The absolute configuration of an epimeric mixture of 1 and 2 was determined by X-ray crystallographic analysis. The compounds isolated were evaluated for their binding propensity in several CNS G protein-coupled receptor assays in vitro
Turbulent Mixing in the Interstellar Medium -- an application for Lagrangian Tracer Particles
We use 3-dimensional numerical simulations of self-gravitating compressible
turbulent gas in combination with Lagrangian tracer particles to investigate
the mixing process of molecular hydrogen (H2) in interstellar clouds. Tracer
particles are used to represent shock-compressed dense gas, which is associated
with H2. We deposit tracer particles in regions of density contrast in excess
of ten times the mean density. Following their trajectories and using
probability distribution functions, we find an upper limit for the mixing
timescale of H2, which is of order 0.3 Myr. This is significantly smaller than
the lifetime of molecular clouds, which demonstrates the importance of the
turbulent mixing of H2 as a preliminary stage to star formation.Comment: 10 pages, 5 figures, conference proceedings "Turbulent Mixing and
Beyond 2007
Casimir Torques between Anisotropic Boundaries in Nematic Liquid Crystals
Fluctuation-induced interactions between anisotropic objects immersed in a
nematic liquid crystal are shown to depend on the relative orientation of these
objects. The resulting long-range ``Casimir'' torques are explicitely
calculated for a simple geometry where elastic effects are absent. Our study
generalizes previous discussions restricted to the case of isotropic walls, and
leads to new proposals for experimental tests of Casimir forces and torques in
nematics.Comment: 4 pages, 1 figur
Multiple-Surrogate Approach to Helicopter Rotor Blade Vibration Reduction
Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/77383/1/AIAA-40291-933.pd
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