21,217 research outputs found
A Heuristic Description of Fast Fourier Transform
Fast Fourier Transform (FFT) is an efficient algorithm to compute the
Discrete Fourier Transform (DFT) and its inverse. In this paper, we pay special
attention to the description of complex-data FFT. We analyze two common
descriptions of FFT and propose a new presentation. Our heuristic description
is helpful for students and programmers to grasp the algorithm entirely and
deeply
Improvement Of Barreto-Voloch Algorithm For Computing th Roots Over Finite Fields
Root extraction is a classical problem in computers algebra. It plays an
essential role in cryptosystems based on elliptic curves. In 2006, Barreto and
Voloch proposed an algorithm to compute th roots in for certain
choices of and . If and they proved that the
complexity of their method is . In this paper, we extend the Barreto-Voloch algorithm to the
general case that , without the restrictions and
. We also specify the conditions that the Barreto-Voloch algorithm
can be preferably applied
A Convergence Theorem for the Graph Shift-type Algorithms
Graph Shift (GS) algorithms are recently focused as a promising approach for
discovering dense subgraphs in noisy data. However, there are no theoretical
foundations for proving the convergence of the GS Algorithm. In this paper, we
propose a generic theoretical framework consisting of three key GS components:
simplex of generated sequence set, monotonic and continuous objective function
and closed mapping. We prove that GS algorithms with such components can be
transformed to fit the Zangwill's convergence theorem, and the sequence set
generated by the GS procedures always terminates at a local maximum, or at
worst, contains a subsequence which converges to a local maximum of the
similarity measure function. The framework is verified by expanding it to other
GS-type algorithms and experimental results
Characterizing A Database of Sequential Behaviors with Latent Dirichlet Hidden Markov Models
This paper proposes a generative model, the latent Dirichlet hidden Markov
models (LDHMM), for characterizing a database of sequential behaviors
(sequences). LDHMMs posit that each sequence is generated by an underlying
Markov chain process, which are controlled by the corresponding parameters
(i.e., the initial state vector, transition matrix and the emission matrix).
These sequence-level latent parameters for each sequence are modeled as latent
Dirichlet random variables and parameterized by a set of deterministic
database-level hyper-parameters. Through this way, we expect to model the
sequence in two levels: the database level by deterministic hyper-parameters
and the sequence-level by latent parameters. To learn the deterministic
hyper-parameters and approximate posteriors of parameters in LDHMMs, we propose
an iterative algorithm under the variational EM framework, which consists of E
and M steps. We examine two different schemes, the fully-factorized and
partially-factorized forms, for the framework, based on different assumptions.
We present empirical results of behavior modeling and sequence classification
on three real-world data sets, and compare them to other related models. The
experimental results prove that the proposed LDHMMs produce better
generalization performance in terms of log-likelihood and deliver competitive
results on the sequence classification problem
Martin points on open manifolds of non-positive curvature
The Martin boundary of a Cartan-Hadamard manifold describes a fine geometric
structure at infinity, which is a sub-space of positive harmonic functions. We
describe conditions which ensure that some points of the sphere at infinity
belong to the Martin boundary as well. In the case of the universal cover of a
compact manifold with Ballmann rank one, we show that Martin points are generic
and of full harmonic measure. The result of this paper provides a partial
answer to an open problem of S. T. Yau
Non-parametric Power-law Data Clustering
It has always been a great challenge for clustering algorithms to
automatically determine the cluster numbers according to the distribution of
datasets. Several approaches have been proposed to address this issue,
including the recent promising work which incorporate Bayesian Nonparametrics
into the -means clustering procedure. This approach shows simplicity in
implementation and solidity in theory, while it also provides a feasible way to
inference in large scale datasets. However, several problems remains unsolved
in this pioneering work, including the power-law data applicability, mechanism
to merge centers to avoid the over-fitting problem, clustering order problem,
e.t.c.. To address these issues, the Pitman-Yor Process based k-means (namely
\emph{pyp-means}) is proposed in this paper. Taking advantage of the Pitman-Yor
Process, \emph{pyp-means} treats clusters differently by dynamically and
adaptively changing the threshold to guarantee the generation of power-law
clustering results. Also, one center agglomeration procedure is integrated into
the implementation to be able to merge small but close clusters and then
adaptively determine the cluster number. With more discussion on the clustering
order, the convergence proof, complexity analysis and extension to spectral
clustering, our approach is compared with traditional clustering algorithm and
variational inference methods. The advantages and properties of pyp-means are
validated by experiments on both synthetic datasets and real world datasets
Critical behaviors and local transformation properties of wave function
We investigate crossing behavior of ground state entanglement Renyi entropies
of quantum critical systems. We find a novel property that the ground state in
one quantum phase cannot be locally transferred to that of another phase, that
means a global transformation is necessary. This also provides a clear evidence
to confirm the long standing expectation that entanglement Renyi entropy
contains more information than entanglement von Neumann entropy. The method of
studying crossing behavior of entanglement Renyi entropies can distinguish
different quantum phases well. We also study the excited states which still
give interesting results.Comment: 4 page
Poker-CNN: A Pattern Learning Strategy for Making Draws and Bets in Poker Games
Poker is a family of card games that includes many variations. We hypothesize
that most poker games can be solved as a pattern matching problem, and propose
creating a strong poker playing system based on a unified poker representation.
Our poker player learns through iterative self-play, and improves its
understanding of the game by training on the results of its previous actions
without sophisticated domain knowledge. We evaluate our system on three poker
games: single player video poker, two-player Limit Texas Hold'em, and finally
two-player 2-7 triple draw poker. We show that our model can quickly learn
patterns in these very different poker games while it improves from zero
knowledge to a competitive player against human experts.
The contributions of this paper include: (1) a novel representation for poker
games, extendable to different poker variations, (2) a CNN based learning model
that can effectively learn the patterns in three different games, and (3) a
self-trained system that significantly beats the heuristic-based program on
which it is trained, and our system is competitive against human expert
players.Comment: 8 page
Gaussian quantum steering and its asymmetry in curved spacetime
We study Gaussian quantum steering and its asymmetry in the background of a
Schwarzschild black hole. We present a Gaussian channel description of quantum
state evolution under the influence of the Hawking radiation. We find that
thermal noise introduced by Hawking effect will destroy the steerability
between an inertial observer Alice and an accelerated observer Bob who hovers
outside the event horizon, while it generates steerability between Bob and a
hypothetical observer anti-Bob inside the event horizon. Unlike entanglement
behaviors in curved spacetime, here the steering from Alice to Bob suffers from
a "sudden death" and the steering from anti-Bob to Bob experiences a "sudden
birth" with increasing Hawking temperature. We also find that the Gaussian
steering is always asymmetric and the maximum steering asymmetry cannot exceed
, which means the state never evolves to an extremal asymmetry state.
Furthermore, we obtain the parameter settings that maximize steering asymmetry
and find that (i) is the critical
point of steering asymmetry, and (ii) the attainment of maximal steering
asymmetry indicates the transition between one-way steerability and both-way
steerability for the two-mode Gaussian state under the influence of Hawking
radiation.Comment: 7 pages, 3 figures, to appear in Phys. Rev.
Tunable Band Topology Reflected by Fractional Quantum Hall States in Two-Dimensional Lattices
Two-dimensional lattice models subjected to an external effective magnetic
field can form nontrivial band topologies characterized by nonzero integer band
Chern numbers. In this Letter, we investigate such a lattice model originating
from the Hofstadter model and demonstrate that the band topology transitions
can be realized by simply introducing tunable longer-range hopping. The rich
phase diagram of band Chern numbers is obtained for the simple rational flux
density and a classification of phases is presented. In the presence of
interactions, the existence of fractional quantum Hall states in both |C|=1 and
|C|>1 bands is confirmed, which can reflect the band topologies in different
phases. In contrast, when our model reduces to a one-dimensional lattice, the
ground states are crucially different from fractional quantum Hall states. Our
results may provide insights into the study of new fractional quantum Hall
states and experimental realizations of various topological phases in optical
lattices.Comment: published version (6 pages, 6 figures, including a supplemental
material
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