3,018 research outputs found
Hawking radiation of charged particles as tunneling from Reissner-Nordstrom-de Sitter black holes with a global monopole
Applying Parikh's semi-classical tunneling method, we consider Hawking
radiation of the charged massive particles as a tunneling process from the
Reissner-Nordstrom-de Sitter black hole with a global monopole. The result
shows that the tunneling rate is related to the change of Bekenstein-Hawking
entropy and the radiant spectrum is not a pure thermal one, but is consistent
with an underlying unitary theory.Comment: 10 pages, no figure, use elsart.cls. Published version in PLB with
correction
Hawking radiation as tunneling from the Kerr and Kerr-Newman black holes
Recent work, which treats the Hawking radiation as a semi-classical tunneling
process at the horizon of the Schwarzschild and Reissner-Nordstrom spacetimes,
indicates that the exact radiant spectrum is no longer pure thermal after
considering the black hole background as dynamical and the conservation of
energy. In this paper, we extend the method to investigate Hawking radiation as
massless particles tunneling across the event horizon of the Kerr black hole
and that of charged particles from the Kerr-Newman black hole by taking into
account the energy conservation, the angular momentum conservation, and the
electric charge conservation. Our results show that when self-gravitation is
considered, the tunneling rate is related to the change of Bekenstein-Hawking
entropy and the derived emission spectrum deviates from the pure thermal
spectrum, but is consistent with an underlying unitary theory.Comment: 10 pages, no figure, Revtex4, typos removed, final version to appear
in PR
Deep Cross-Modal Hashing
Due to its low storage cost and fast query speed, cross-modal hashing (CMH)
has been widely used for similarity search in multimedia retrieval
applications. However, almost all existing CMH methods are based on
hand-crafted features which might not be optimally compatible with the
hash-code learning procedure. As a result, existing CMH methods with
handcrafted features may not achieve satisfactory performance. In this paper,
we propose a novel cross-modal hashing method, called deep crossmodal hashing
(DCMH), by integrating feature learning and hash-code learning into the same
framework. DCMH is an end-to-end learning framework with deep neural networks,
one for each modality, to perform feature learning from scratch. Experiments on
two real datasets with text-image modalities show that DCMH can outperform
other baselines to achieve the state-of-the-art performance in cross-modal
retrieval applications.Comment: 12 page
Asymmetric Deep Supervised Hashing
Hashing has been widely used for large-scale approximate nearest neighbor
search because of its storage and search efficiency. Recent work has found that
deep supervised hashing can significantly outperform non-deep supervised
hashing in many applications. However, most existing deep supervised hashing
methods adopt a symmetric strategy to learn one deep hash function for both
query points and database (retrieval) points. The training of these symmetric
deep supervised hashing methods is typically time-consuming, which makes them
hard to effectively utilize the supervised information for cases with
large-scale database. In this paper, we propose a novel deep supervised hashing
method, called asymmetric deep supervised hashing (ADSH), for large-scale
nearest neighbor search. ADSH treats the query points and database points in an
asymmetric way. More specifically, ADSH learns a deep hash function only for
query points, while the hash codes for database points are directly learned.
The training of ADSH is much more efficient than that of traditional symmetric
deep supervised hashing methods. Experiments show that ADSH can achieve
state-of-the-art performance in real applications
Homeomorphisms of 3-manifolds and the realization of Nielsen Number
The Nielsen Conjecture for Homeomorphisms asserts that any homeomorphism
of a closed manifold is isotopic to a map realizing the Nielsen number of ,
which is a lower bound for the number of fixed points among all maps homotopic
to . The main theorem of this paper proves this conjecture for all
orientation preserving maps on geometric or Haken 3-manifolds. It will also be
shown that on many manifolds all maps are isotopic to fixed point free maps.
The proof is based on the understanding of homeomorphisms on 2-orbifolds and
3-manifolds. Thurston's classification of surface homeomorphisms will be
generalized to 2-dimensional orbifolds, which is used to study fiber preserving
maps of Seifert fiber spaces. Maps on most Seifert fiber spaces are indeed
isotopic to fiber preserving maps, with the exception of four manifolds and
orientation reversing maps on lens spaces or . It will also be determined
exactly which manifolds have a unique Seifert fibration up to isotopy. These
informations will be used to deform a map to certain standard map on each piece
of the JSJ decomposition, as well as on the neighborhood of the decomposition
tori, which will make it possible to shrink each fixed point class to a single
point, and remove inessential fixed point classes
Deep Discrete Supervised Hashing
Hashing has been widely used for large-scale search due to its low storage
cost and fast query speed. By using supervised information, supervised hashing
can significantly outperform unsupervised hashing. Recently, discrete
supervised hashing and deep hashing are two representative progresses in
supervised hashing. On one hand, hashing is essentially a discrete optimization
problem. Hence, utilizing supervised information to directly guide discrete
(binary) coding procedure can avoid sub-optimal solution and improve the
accuracy. On the other hand, deep hashing, which integrates deep feature
learning and hash-code learning into an end-to-end architecture, can enhance
the feedback between feature learning and hash-code learning. The key in
discrete supervised hashing is to adopt supervised information to directly
guide the discrete coding procedure in hashing. The key in deep hashing is to
adopt the supervised information to directly guide the deep feature learning
procedure. However, there have not existed works which can use the supervised
information to directly guide both discrete coding procedure and deep feature
learning procedure in the same framework. In this paper, we propose a novel
deep hashing method, called deep discrete supervised hashing (DDSH), to address
this problem. DDSH is the first deep hashing method which can utilize
supervised information to directly guide both discrete coding procedure and
deep feature learning procedure, and thus enhance the feedback between these
two important procedures. Experiments on three real datasets show that DDSH can
outperform other state-of-the-art baselines, including both discrete hashing
and deep hashing baselines, for image retrieval
Hawking Radiation of Charged Particles as Tunneling from Higher Dimensional Reissner-Nordstrom-de Sitter Black Holes
Recent work that treats the Hawking radiation as a semi-classical tunnelling
process from the four-dimensional Schwarzschild and Reissner-Nordstrom black
holes is extended to the case of higher dimensional Reissner-Nordstrom-de
Sitter black holes. The result shows that the tunnelling rate is related to the
change of Bekenstein-Hawking entropy and the exact radiant spectrum is no
longer precisely thermal after considering the black hole background as
dynamical and incorporating the self-gravitation effect of the emitted
particles when the energy conservation and electric charge conservation are
taken into account.Comment: 13 pages, no figure, enlarged versio
On the Evaluation Metric for Hashing
Due to its low storage cost and fast query speed, hashing has been widely
used for large-scale approximate nearest neighbor (ANN) search. Bucket search,
also called hash lookup, can achieve fast query speed with a sub-linear time
cost based on the inverted index table constructed from hash codes. Many
metrics have been adopted to evaluate hashing algorithms. However, all existing
metrics are improper to evaluate the hash codes for bucket search. On one hand,
all existing metrics ignore the retrieval time cost which is an important
factor reflecting the performance of search. On the other hand, some of them,
such as mean average precision (MAP), suffer from the uncertainty problem as
the ranked list is based on integer-valued Hamming distance, and are
insensitive to Hamming radius as these metrics only depend on relative Hamming
distance. Other metrics, such as precision at Hamming radius R, fail to
evaluate global performance as these metrics only depend on one specific
Hamming radius. In this paper, we first point out the problems of existing
metrics which have been ignored by the hashing community, and then propose a
novel evaluation metric called radius aware mean average precision (RAMAP) to
evaluate hash codes for bucket search. Furthermore, two coding strategies are
also proposed to qualitatively show the problems of existing metrics.
Experiments demonstrate that our proposed RAMAP can provide more proper
evaluation than existing metrics
Deep Multi-Index Hashing for Person Re-Identification
Traditional person re-identification (ReID) methods typically represent
person images as real-valued features, which makes ReID inefficient when the
gallery set is extremely large. Recently, some hashing methods have been
proposed to make ReID more efficient. However, these hashing methods will
deteriorate the accuracy in general, and the efficiency of them is still not
high enough. In this paper, we propose a novel hashing method, called deep
multi-index hashing (DMIH), to improve both efficiency and accuracy for ReID.
DMIH seamlessly integrates multi-index hashing and multi-branch based networks
into the same framework. Furthermore, a novel block-wise multi-index hashing
table construction approach and a search-aware multi-index (SAMI) loss are
proposed in DMIH to improve the search efficiency. Experiments on three widely
used datasets show that DMIH can outperform other state-of-the-art baselines,
including both hashing methods and real-valued methods, in terms of both
efficiency and accuracy.Comment: 10 pages, 6 figures, 2 table
Achirality of knots and links
We will develop various methods, some are of geometric nature and some are of
algebraic nature, to detect the various achiralities of knots and links in
. For example, we show that the twisted Whitehead double of a knot is
achiral if and only if the double is the unknot or the figure eight knot, and
we show that all non-trivial links with crossings are not achiral
except the Borromean rings. A simple procedure for calculating the
-function is given in terms of a crossing change formula and its initial
values.Comment: amstex, 28 pages with 10 figures. Results in Section 5 are
substantially improve
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