2,891 research outputs found
Numerical Evidence for Multiplicative Logarithmic Corrections from Marginal Operators
Field theory calculations predict multiplicative logarithmic corrections to
correlation functions from marginally irrelevant operators. However, for the
numerically most suitable model - the spin-1/2 chain - these corrections have
been controversial. In this paper, the spin-spin correlation function of the
antiferromagnetic spin-1/2 chain is calculated numerically in the presence of a
next nearest neighbor coupling J2 for chains of up to 32 sites. By varying the
coupling strength J2 we can control the effect of the marginal operator, and
our results unambiguously confirm the field theory predictions. The critical
value at which the marginal operator vanishes has been determined to be at J2 =
0.241167 +/- 0.000005J.Comment: revised paper with extended data-analysis. 5 pages, using revtex with
4 embedded figures (included with macro). A complete postscript file with all
figures + text (5 pages) is available from
http://FY.CHALMERS.SE/~eggert/marginal.ps or by request from
[email protected]
Improving Small Object Proposals for Company Logo Detection
Many modern approaches for object detection are two-staged pipelines. The
first stage identifies regions of interest which are then classified in the
second stage. Faster R-CNN is such an approach for object detection which
combines both stages into a single pipeline. In this paper we apply Faster
R-CNN to the task of company logo detection. Motivated by its weak performance
on small object instances, we examine in detail both the proposal and the
classification stage with respect to a wide range of object sizes. We
investigate the influence of feature map resolution on the performance of those
stages.
Based on theoretical considerations, we introduce an improved scheme for
generating anchor proposals and propose a modification to Faster R-CNN which
leverages higher-resolution feature maps for small objects. We evaluate our
approach on the FlickrLogos dataset improving the RPN performance from 0.52 to
0.71 (MABO) and the detection performance from 0.52 to 0.67 (mAP).Comment: 8 Pages, ICMR 201
Non-Collinear Ferromagnetic Luttinger Liquids
The presence of electron-electron interactions in one dimension profoundly
changes the properties of a system. The separation of charge and spin degrees
of freedom is just one example. We consider what happens when a system
consisting of a ferromagnetic region of non-collinearity, i.e. a domain wall,
is coupled to interacting electrons in one-dimension (more specifically a
Luttinger liquid). The ferromagnetism breaks spin charge separation and the
presence of the domain wall introduces a spin dependent scatterer into the
problem. The absence of spin charge separation and the effects of the electron
correlations results in very different behaviour for the excitations in the
system and for spin-transfer-torque effects in this model.Comment: 6 pages, submitted to Journal of Physics: Conference Series for JEMS
201
Quasi-analytical formulation for calculation of infiltration and runoff
Prepared for USDA Forest Service, Rocky Mountain Forest and Range Experiment Station.CER81-82-86.December 1981.Bibliography: pages 41-42
Correlation Functions and Coulomb Blockade of Interacting Fermions at Finite Temperature and Size
We present explicit expressions for the correlation functions of interacting
fermions in one dimension which are valid for arbitrary system sizes and
temperatures. The result applies to a number of very different strongly
correlated systems, including mesoscopic quantum wires, quantum Hall edges,
spin chains and quasi-one-dimensional metals. It is for example possible to
calculate Coulomb blockade oscillations from our expression and determine their
dependence on interaction strength and temperature. Numerical simulations show
excellent agreement with the analytical results.Comment: 10 pages in revtex format including 2 embedded figures (using epsf).
The latest complete postscript file is available from
http://fy.chalmers.se/~eggert/papers/corrfcn.ps or by request from
[email protected]
Interplay of Coulomb blockade and Aharonov-Bohm resonances in a Luttinger liquid
We consider a ring of strongly interacting electrons connected to two
external leads by tunnel junctions. By studying the positions of conductance
resonances as a function of gate voltage and magnetic flux the interaction
parameter can be determined experimentally. For a finite ring the minimum
conductance is strongly influenced by device geometry and electron-electron
interactions. In particular, if the tunnel junctions are close to one another
the interaction-related orthogonality catastrophe is suppressed and the valley
current is unexpectedly large.Comment: 10 page
Thermodynamical Properties of a Spin 1/2 Heisenberg Chain Coupled to Phonons
We performed a finite-temperature quantum Monte Carlo simulation of the
one-dimensional spin-1/2 Heisenberg model with nearest-neighbor interaction
coupled to Einstein phonons. Our method allows to treat easily up to 100
phonons per site and the results presented are practically free from truncation
errors. We studied in detail the magnetic susceptibility, the specific heat,
the phonon occupation, the dimerization, and the spin-correlation function for
various spin-phonon couplings and phonon frequencies. In particular we give
evidence for the transition from a gapless to a massive phase by studying the
finite-size behavior of the susceptibility. We also show that the dimerization
is proportional to for .Comment: 10 pages, 17 Postscript Figure
From Tomonaga-Luttinger to Fermi liquid in transport through a tunneling barrier
Finite length of a one channel wire results in crossover from a
Tomonaga-Luttinger to Fermi liquid behavior with lowering energy scale. In
condition that voltage drop mostly occurs across a tunnel barrier inside
the wire we found coefficients of temperature/voltage expansion of low energy
conductance as a function of constant of interaction, right and left traversal
times. At higher voltage the finite length contribution exhibits oscillations
related to both traversal times and becomes a slowly decaying correction to the
scale-invariant dependence of the conductance.Comment: 12 pages of RevTex file and 1 PS file figur
Photon-Photon and Photon-Hadron Physics at Relativistic Heavy Ion Colliders
Due to the coherence of all the protons in a nucleus, there are very strong
electromagnetic fields of short duration in relativistic heavy ion collisions.
They give rise to quasireal photon-photon and photon-nucleus collisions with a
large flux. RHIC will begin its experimental program this year and such types
of collisions will be studied experimentally at the STAR detector. RHIC will
have the highest flux of (quasireal) photons up to now in the GeV region. At
the LHC the invariant mass range available in gamma-gamma-interactions will be
of the order of 100 GeV, i.e., in the range currently available at LEP2, but
with a higher gamma-gamma-luminosity. Therefore one has there also the
potential to study new physics. (Quasireal) photon-hadron (i.e.,
photon-nucleus) interactions can be studied as well, similar to HERA, at higher
invariant masses. Vector mesons can be produced coherently through
photon-Pomeron and photon-meson interactions in exclusive reactions such as A+A
-> A+A+V, where A is the heavy ion and V=rho,omega,phi or J/Psi.Comment: 6 pages, to be published in the proceedings of the Photon'99
conferenc
Recognition of 3-D Objects from Multiple 2-D Views by a Self-Organizing Neural Architecture
The recognition of 3-D objects from sequences of their 2-D views is modeled by a neural architecture, called VIEWNET that uses View Information Encoded With NETworks. VIEWNET illustrates how several types of noise and varialbility in image data can be progressively removed while incornplcte image features are restored and invariant features are discovered using an appropriately designed cascade of processing stages. VIEWNET first processes 2-D views of 3-D objects using the CORT-X 2 filter, which discounts the illuminant, regularizes and completes figural boundaries, and removes noise from the images. Boundary regularization and cornpletion are achieved by the same mechanisms that suppress image noise. A log-polar transform is taken with respect to the centroid of the resulting figure and then re-centered to achieve 2-D scale and rotation invariance. The invariant images are coarse coded to further reduce noise, reduce foreshortening effects, and increase generalization. These compressed codes are input into a supervised learning system based on the fuzzy ARTMAP algorithm. Recognition categories of 2-D views are learned before evidence from sequences of 2-D view categories is accumulated to improve object recognition. Recognition is studied with noisy and clean images using slow and fast learning. VIEWNET is demonstrated on an MIT Lincoln Laboratory database of 2-D views of jet aircraft with and without additive noise. A recognition rate of 90% is achieved with one 2-D view category and of 98.5% correct with three 2-D view categories.National Science Foundation (IRI 90-24877); Office of Naval Research (N00014-91-J-1309, N00014-91-J-4100, N00014-92-J-0499); Air Force Office of Scientific Research (F9620-92-J-0499, 90-0083
- …