32,566 research outputs found
Electrons and Heavy Quark at PHENIX Detector
Measurement of heavy quark production is one of the tools used to investigate
the matter produced in extremely hot and dense conditions in heavy ion
collisions at RHIC. The PHENIX experiment has measured mid-rapidity transverse
momentum spectra of electrons. After subtracting the photonic background
contribution, the electron spectra are mainly due to semileptonic decays of
hadrons containing heavy quarks and therefore provide a measurement of heavy
quark production and its energy loss in hot and dense matter. This paper will
present the technique used by the PHENIX experiment and recent results on heavy
quark production in p+p, d+Au and Au+Au collisions at sqrt{s_NN}=200 GeV.Comment: 15 pages, 10 figures. To be present in proceedings of the 22nd Winter
Workshop on Nuclear Dynamics (March 11-18, 2006
Constraining the Doublet Left-Right Model
Left-Right Models (LRM) attempt at giving an understanding of the violation
of parity (or charge-conjugation) by the weak interactions in the SM through a
similar description of left- and right-handed currents at high energies. The
spontaneous symmetry breaking of the LRM gauge group is triggered by an
enlarged Higgs sector, usually consisting of two triplet fields (left-right
symmetry breaking) and a bidoublet (electroweak symmetry breaking). I
reconsider an alternative LRM with doublet instead of triplet fields. After
explaining some features of this model, I discuss constraints on its parameters
using electroweak precision observables (combined using the CKMfitter
frequentist statistical framework) and neutral-meson mixing observables.Comment: Proceedings of the workshop "Flavorful Ways to New Physics", 28-31
October 2014, Freudenstadt, German
Local Conformal Rigidity in Codimension 5
In this paper, for an immersion of an -dimensional Riemannian manifold
into -Euclidean space we give a sufficient condition on so that,
in case , any immersion of into -Euclidean space that
induces on a metric that is conformal to the metric induced by is
locally obtained, in a dense subset of , by a composition of and a
conformal immersion from an open subset of -Euclidean space into an open
subset of -Euclidean space. Our result extends a theorem for
hypersurfaces due to M. Dajczer and E. Vergasta. The restriction on the
codimension is related to a basic lemma in the theory of rigidity obtained by
M. do Carmo and M. Dajczer.Comment: 16 page
Cr-invariants for surfaces in 4-space
We establish cross-ratio invariants for surfaces in 4-space in an analogous
way to Uribe-Vargas's work for surfaces in 3-space. We study the geometric
locii of local and multi-local singularities of ortogonal projections of the
surface. The cross-ratio invariants at -points are used to recover two
moduli in the 4-jet of the projective parametrization of the surface and show
the stable configurations of asymptotic curves.Comment: 22 page
Moving frames and the characterization of curves that lie on a surface
In this work we are interested in the characterization of curves that belong
to a given surface. To the best of our knowledge, there is no known general
solution to this problem. Indeed, a solution is only available for a few
examples: planes, spheres, or cylinders. Generally, the characterization of
such curves, both in Euclidean () and in Lorentz-Minkowski ()
spaces, involves an ODE relating curvature and torsion. However, by equipping a
curve with a relatively parallel moving frame, Bishop was able to characterize
spherical curves in through a linear equation relating the coefficients
which dictate the frame motion. Here we apply these ideas to surfaces that are
implicitly defined by a smooth function, , by reinterpreting
the problem in the context of the metric given by the Hessian of , which is
not always positive definite. So, we are naturally led to the study of curves
in . We develop a systematic approach to the construction of Bishop
frames by exploiting the structure of the normal planes induced by the casual
character of the curve, present a complete characterization of spherical curves
in , and apply it to characterize curves that belong to a non-degenerate
Euclidean quadric. We also interpret the casual character that a curve may
assume when we pass from to and finally establish a criterion for
a curve to lie on a level surface of a smooth function, which reduces to a
linear equation when the Hessian is constant.Comment: 22 pages (23 in the published version), 3 figures; this version is
essentially the same as the published on
Characterization of curves that lie on a geodesic sphere or on a totally geodesic hypersurface in a hyperbolic space or in a sphere
The consideration of the so-called rotation minimizing frames allows for a
simple and elegant characterization of plane and spherical curves in Euclidean
space via a linear equation relating the coefficients that dictate the frame
motion. In this work, we extend these investigations to characterize curves
that lie on a geodesic sphere or totally geodesic hypersurface in a Riemannian
manifold of constant curvature. Using that geodesic spherical curves are normal
curves, i.e., they are the image of an Euclidean spherical curve under the
exponential map, we are able to characterize geodesic spherical curves in
hyperbolic spaces and spheres through a non-homogeneous linear equation.
Finally, we also show that curves on totally geodesic hypersurfaces, which play
the role of hyperplanes in Riemannian geometry, should be characterized by a
homogeneous linear equation. In short, our results give interesting and
significant similarities between hyperbolic, spherical, and Euclidean
geometries.Comment: 15 pages, 3 figures; comments are welcom
Characterization of manifolds of constant curvature by spherical curves
It is known that the so-called rotation minimizing (RM) frames allow for a
simple and elegant characterization of geodesic spherical curves in Euclidean,
hyperbolic, and spherical spaces through a certain linear equation involving
the coefficients that dictate the RM frame motion (da Silva, da Silva in
Mediterr J Math 15:70, 2018). Here, we shall prove the converse, i.e., we show
that if all geodesic spherical curves on a Riemannian manifold are
characterized by a certain linear equation, then all the geodesic spheres with
a sufficiently small radius are totally umbilical and, consequently, the given
manifold has constant sectional curvature. We also furnish two other
characterizations in terms of (i) an inequality involving the mean curvature of
a geodesic sphere and the curvature function of their curves and (ii) the
vanishing of the total torsion of closed spherical curves in the case of
three-dimensional manifolds. Finally, we also show that the same results are
valid for semi-Riemannian manifolds of constant sectional curvature.Comment: To appear in Annali di Matematica Pura ed Applicat
Dynamic Difficulty Adjustment on MOBA Games
This paper addresses the dynamic difficulty adjustment on MOBA games as a way
to improve the player's entertainment. Although MOBA is currently one of the
most played genres around the world, it is known as a game that offer less
autonomy, more challenges and consequently more frustration. Due to these
characteristics, the use of a mechanism that performs the difficulty balance
dynamically seems to be an interesting alternative to minimize and/or avoid
that players experience such frustrations. In this sense, this paper presents a
dynamic difficulty adjustment mechanism for MOBA games. The main idea is to
create a computer controlled opponent that adapts dynamically to the player
performance, trying to offer to the player a better game experience. This is
done by evaluating the performance of the player using a metric based on some
game features and switching the difficulty of the opponent's artificial
intelligence behavior accordingly. Quantitative and qualitative experiments
were performed and the results showed that the system is capable of adapting
dynamically to the opponent's skills. In spite of that, the qualitative
experiments with users showed that the player's expertise has a greater
influence on the perception of the difficulty level and dynamic adaptation.Comment: 103-12
A Tutor Agent for MOBA Games
Digital games have become a key player in the entertainment industry,
attracting millions of new players each year. In spite of that, novice players
may have a hard time when playing certain types of games, such as MOBAs and
MMORPGs, due to their steep learning curves and not so friendly online
communities. In this paper, we present an approach to help novice players in
MOBA games overcome these problems. An artificial intelligence agent plays
alongside the player analyzing his/her performance and giving tips about the
game. Experiments performed with the game {\em League of Legends} show the
potential of this approach
On the Development of Intelligent Agents for MOBA Games
Multiplayer Online Battle Arena (MOBA) is one of the most played game genres
nowadays. With the increasing growth of this genre, it becomes necessary to
develop effective intelligent agents to play alongside or against human
players. In this paper we address the problem of agent development for MOBA
games. We implement a two-layered architecture agent that handles both
navigation and game mechanics. This architecture relies on the use of Influence
Maps, a widely used approach for tactical analysis. Several experiments were
performed using {\em League of Legends} as a testbed, and show promising
results in this highly dynamic real-time context
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