18,915 research outputs found
Asymptotics of spectral function of lower energy forms and Bergman kernel of semi-positive and big line bundles
In this paper we study the asymptotic behaviour of the spectral function
corresponding to the lower part of the spectrum of the Kodaira Laplacian on
high tensor powers of a holomorphic line bundle. This implies a full asymptotic
expansion of this function on the set where the curvature of the line bundle is
non-degenerate. As application we obtain the Bergman kernel asymptotics for
adjoint semi-positive line bundles over complete Kaehler manifolds, on the set
where the curvature is positive. We also prove the asymptotics for big line
bundles endowed with singular Hermitian metrics with strictly positive
curvature current. In this case the full asymptotics holds outside the singular
locus of the metric.Comment: 71 pages; v.2 is a final update to agree with the published pape
On the stability of equivariant embedding of compact CR manifolds with circle action
We prove the stability of the equivariant embedding of compact strictly
pseudoconvex CR manifolds with transversal CR circle action under circle
invariant perturbations of the CR structures.Comment: 21 pages, final versio
Auction-Based Coopetition between LTE Unlicensed and Wi-Fi
Motivated by the recent efforts in extending LTE to the unlicensed spectrum,
we propose a novel spectrum sharing framework for the coopetition (i.e.,
cooperation and competition) between LTE and Wi-Fi in the unlicensed band.
Basically, the LTE network can choose to work in one of the two modes: in the
competition mode, it randomly accesses an unlicensed channel, and interferes
with the Wi-Fi access point using the same channel; in the cooperation mode, it
delivers traffic for the Wi-Fi users in exchange for the exclusive access of
the corresponding channel. Because the LTE network works in an
interference-free manner in the cooperation mode, it can achieve a much larger
data rate than that in the competition mode, which allows it to effectively
serve both its own users and the Wi-Fi users. We design a second-price reverse
auction mechanism, which enables the LTE provider and the Wi-Fi access point
owners (APOs) to effectively negotiate the operation mode. Specifically, the
LTE provider is the auctioneer (buyer), and the APOs are the bidders (sellers)
who compete to sell their channel access opportunities to the LTE provider. In
Stage I of the auction, the LTE provider announces a reserve rate. In Stage II
of the auction, the APOs submit their bids. We show that the auction involves
allocative externalities, i.e., the cooperation between the LTE provider and
one APO benefits other APOs who are not directly involved in this cooperation.
As a result, a particular APO's willingness to cooperate is affected by its
belief about other APOs' willingness to cooperate. This makes our analysis much
more challenging than that of the conventional second-price auction, where
bidding truthfully is a weakly dominant strategy. We show that the APOs have a
unique form of the equilibrium bidding strategies in Stage II, based on which
we analyze the LTE provider's optimal reserve rate in Stage I.Comment: 32 page
Geometry-Oblivious FMM for Compressing Dense SPD Matrices
We present GOFMM (geometry-oblivious FMM), a novel method that creates a
hierarchical low-rank approximation, "compression," of an arbitrary dense
symmetric positive definite (SPD) matrix. For many applications, GOFMM enables
an approximate matrix-vector multiplication in or even time,
where is the matrix size. Compression requires storage and work.
In general, our scheme belongs to the family of hierarchical matrix
approximation methods. In particular, it generalizes the fast multipole method
(FMM) to a purely algebraic setting by only requiring the ability to sample
matrix entries. Neither geometric information (i.e., point coordinates) nor
knowledge of how the matrix entries have been generated is required, thus the
term "geometry-oblivious." Also, we introduce a shared-memory parallel scheme
for hierarchical matrix computations that reduces synchronization barriers. We
present results on the Intel Knights Landing and Haswell architectures, and on
the NVIDIA Pascal architecture for a variety of matrices.Comment: 13 pages, accepted by SC'1
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