25,494 research outputs found
Finite Density Algorithm in Lattice QCD -- a Canonical Ensemble Approach
I will review the finite density algorithm for lattice QCD based on finite
chemical potential and summarize the associated difficulties. I will propose a
canonical ensemble approach which projects out the finite baryon number sector
from the fermion determinant. For this algorithm to work, it requires an
efficient method for calculating the fermion determinant and a Monte Carlo
algorithm which accommodates unbiased estimate of the probability. I shall
report on the progress made along this direction with the Pad\'{e} - Z
estimator of the determinant and its implementation in the newly developed
Noisy Monte Carlo algorithm.Comment: Invited talk at Nankai Symposium on Mathematical Physics, Tianjin,
Oct. 2001, 18 pages, 3 figures; expanded and references adde
Coplanar Circumbinary Debris Disks
We present resolved Herschel images of circumbinary debris disks in the alpha
CrB (HD139006) and beta Tri (HD13161) systems. We find that both disks are
consistent with being aligned with the binary orbital planes. Though secular
perturbations from the binary can align the disk, in both cases the alignment
time at the distances at which the disk is resolved is greater than the stellar
age, so we conclude that the coplanarity was primordial. Neither disk can be
modelled as a narrow ring, requiring extended radial distributions. To satisfy
both the Herschel and mid-IR images of the alpha CrB disk, we construct a model
that extends from 1-300AU, whose radial profile is broadly consistent with a
picture where planetesimal collisions are excited by secular perturbations from
the binary. However, this model is also consistent with stirring by other
mechanisms, such as the formation of Pluto-sized objects. The beta Tri disk
model extends from 50-400AU. A model with depleted (rather than empty) inner
regions also reproduces the observations and is consistent with binary and
other stirring mechanisms. As part of the modelling process, we find that the
Herschel PACS beam varies by as much as 10% at 70um and a few % at 100um. The
70um variation can therefore hinder image interpretation, particularly for
poorly resolved objects. The number of systems in which circumbinary debris
disk orientations have been compared with the binary plane is now four. More
systems are needed, but a picture in which disks around very close binaries
(alpha CrB, beta Tri, and HD 98800, with periods of a few weeks to a year) are
aligned, and disks around wider binaries (99 Her, with a 50 yr period) are
misaligned, may be emerging. This picture is qualitatively consistent with the
expectation that the protoplanetary disks from which the debris emerged are
more likely to be aligned if their binaries have shorter periods.Comment: accepted to MNRA
Computing the Loewner driving process of random curves in the half plane
We simulate several models of random curves in the half plane and numerically
compute their stochastic driving process (as given by the Loewner equation).
Our models include models whose scaling limit is the Schramm-Loewner evolution
(SLE) and models for which it is not. We study several tests of whether the
driving process is Brownian motion. We find that just testing the normality of
the process at a fixed time is not effective at determining if the process is
Brownian motion. Tests that involve the independence of the increments of
Brownian motion are much more effective. We also study the zipper algorithm for
numerically computing the driving function of a simple curve. We give an
implementation of this algorithm which runs in a time O(N^1.35) rather than the
usual O(N^2), where N is the number of points on the curve.Comment: 20 pages, 4 figures. Changes to second version: added new paragraph
to conclusion section; improved figures cosmeticall
Variations of Little Higgs Models and their Electroweak Constraints
We calculate the tree-level electroweak precision constraints on a wide class
of little Higgs models including: variations of the Littlest Higgs SU(5)/SO(5),
SU(6)/Sp(6), and SU(4)^4/SU(3)^4. By performing a global fit to the precision
data we find that for generic regions of the parameter space the bound on the
symmetry breaking scale f is several TeV, where we have kept the normalization
of f constant in the different models. For example, the ``minimal''
implementation of SU(6)/Sp(6) is bounded by f>3.0 TeV throughout most of the
parameter space, and SU(4)^4/SU(3)^4 is bounded by f^2 = f_1^2+f_2^2 > (4.2
TeV)^2. In certain models, such as SU(4)^4/SU(3)^4, a large f does not directly
imply a large amount of fine tuning since the heavy fermion masses that
contribute to the Higgs mass can be lowered below f for a carefully chosen set
of parameters. We also find that for certain models (or variations) there exist
regions of parameter space in which the bound on f can be lowered into the
range 1-2 TeV. These regions are typically characterized by a small mixing
between heavy and standard model gauge bosons, and a small (or vanishing)
coupling between heavy U(1) gauge bosons and the light fermions. Whether such a
region of parameter space is natural or not is ultimately contingent on the UV
completion.Comment: 32 pages, 13 figures; revised discussion of SU(4)^4/SU(3)^4 model,
bound on f is slightly highe
Mott transition in lattice boson models
We use mathematically rigorous perturbation theory to study the transition
between the Mott insulator and the conjectured Bose-Einstein condensate in a
hard-core Bose-Hubbard model. The critical line is established to lowest order
in the tunneling amplitude.Comment: 20 page
REALTIME FRAUD DETECTION IN THE BANKING SECTOR USING DATA MINING TECHNIQUES/ALGORITHM
Abstract—The banking sector is a very important sector in
our present day generation where almost every human has to
deal with the bank either physically or online. In dealing with
the banks, the customers and the banks face the chances of
been trapped by fraudsters. Examples of fraud include
insurance fraud, credit card fraud, accounting fraud, etc.
Detection of fraudulent activity is thus critical to control these
costs. This paper hereby addresses bank fraud detection via
the use of data-mining techniques; association, clustering,
forecasting, and classification to analyze the customer data in
order to identify the patterns that can lead to frauds. Upon
identification of the patterns, adding a higher level of
verification/authentication to banking processes can be added
Keywords: Data mining techniques, banking sector, fraud, and
authentication
Professional service firms are relationship marketers: But does size matter?
There are few research-based insights into professional service firms’ (PSFs) contemporary marketing practices. This is unfortunate as the professional services sector is a key contributor to growth in Australian and other economies around the world. As professional services are unique in a number of ways and their operations and marketing activities inextricably intertwined, the present study investigated the extent to which PSFs practice marketing and whether this differs according to size. Depth interviews were held with thirty seven Australian senior managers in four key industries. We examined the extent of relationship marketing, conceptualised at an overall managerial level as well as four sub-practices identified in research by Coviello and colleagues. We found relationship management and interaction marketing were the most common practices, which is consistent with the inseparability concept, and that relationship management and database marketing were more common in larger firms, which is consistent with their relative resource strength
Charge-ordered ferromagnetic phase in manganites
A mechanism for charge-ordered ferromagnetic phase in manganites is proposed.
The mechanism is based on the double exchange in the presence of diagonal
disorder. It is modeled by a combination of the Ising double-exchange and the
Falicov-Kimball model. Within the dynamical mean-field theory the charge and
spin correlation function are explicitely calculated. It is shown that the
system exhibits two successive phase transitions. The first one is the
ferromagnetic phase transition, and the second one is a charge ordering. As a
result a charge-ordered ferromagnetic phase is stabilized at low temperature.Comment: To appear in Phys. Rev.
Insights into neutralization of animal viruses gained from study of influenza virus
It has long been known that the binding of antibodies to viruses can result in a loss of infectivity, or neutralization, but little is understood of the mechanism or mechanisms of this process. This is probably because neutralization is a multifactorial phenomenon depending upon the nature of the virus itself, the particular antigenic site involved, the isotype of immunoglobulin and the ratio of virus to immunoglobulin (see below). Thus not only is it likely that neutralization of one virus will differ from another but that changing the circumstances of neutralization can change the mechanism itself. To give coherence to the topic we are concentrating this review on one virus, influenza type A which is itself well studied and reasonably well understood [1–3]. Reviews of the older literature can be found in references 4 to 7
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