9,271 research outputs found
Asymptotic Freedom and Bound States in Hamiltonian Dynamics
We study a model of asymptotically free theories with bound states using the
similarity renormalization group for hamiltonians. We find that the
renormalized effective hamiltonians can be approximated in a large range of
widths by introducing similarity factors and the running coupling constant.
This approximation loses accuracy for the small widths on the order of the
bound state energy and it is improved by using the expansion in powers of the
running coupling constant. The coupling constant for small widths is order 1.
The small width effective hamiltonian is projected on a small subset of the
effective basis states. The resulting small matrix is diagonalized and the
exact bound state energy is obtained with accuracy of the order of 10% using
the first three terms in the expansion. We briefly describe options for
improving the accuracy.Comment: plain latex file, 15 pages, 6 latex figures 1 page each, 1 tabl
Bayesian Optimisation for Safe Navigation under Localisation Uncertainty
In outdoor environments, mobile robots are required to navigate through
terrain with varying characteristics, some of which might significantly affect
the integrity of the platform. Ideally, the robot should be able to identify
areas that are safe for navigation based on its own percepts about the
environment while avoiding damage to itself. Bayesian optimisation (BO) has
been successfully applied to the task of learning a model of terrain
traversability while guiding the robot through more traversable areas. An
issue, however, is that localisation uncertainty can end up guiding the robot
to unsafe areas and distort the model being learnt. In this paper, we address
this problem and present a novel method that allows BO to consider localisation
uncertainty by applying a Gaussian process model for uncertain inputs as a
prior. We evaluate the proposed method in simulation and in experiments with a
real robot navigating over rough terrain and compare it against standard BO
methods.Comment: To appear in the proceedings of the 18th International Symposium on
Robotics Research (ISRR 2017
Systematic Renormalization in Hamiltonian Light-Front Field Theory: The Massive Generalization
Hamiltonian light-front field theory can be used to solve for hadron states
in QCD. To this end, a method has been developed for systematic renormalization
of Hamiltonian light-front field theories, with the hope of applying the method
to QCD. It assumed massless particles, so its immediate application to QCD is
limited to gluon states or states where quark masses can be neglected. This
paper builds on the previous work by including particle masses
non-perturbatively, which is necessary for a full treatment of QCD. We show
that several subtle new issues are encountered when including masses
non-perturbatively. The method with masses is algebraically and conceptually
more difficult; however, we focus on how the methods differ. We demonstrate the
method using massive phi^3 theory in 5+1 dimensions, which has important
similarities to QCD.Comment: 7 pages, 2 figures. Corrected error in Eq. (11), v3: Added extra
disclaimer after Eq. (2), and some clarification at end of Sec. 3.3. Final
published versio
Systematic Renormalization in Hamiltonian Light-Front Field Theory
We develop a systematic method for computing a renormalized light-front field
theory Hamiltonian that can lead to bound states that rapidly converge in an
expansion in free-particle Fock-space sectors. To accomplish this without
dropping any Fock sectors from the theory, and to regulate the Hamiltonian, we
suppress the matrix elements of the Hamiltonian between free-particle
Fock-space states that differ in free mass by more than a cutoff. The cutoff
violates a number of physical principles of the theory, and thus the
Hamiltonian is not just the canonical Hamiltonian with masses and couplings
redefined by renormalization. Instead, the Hamiltonian must be allowed to
contain all operators that are consistent with the unviolated physical
principles of the theory. We show that if we require the Hamiltonian to produce
cutoff-independent physical quantities and we require it to respect the
unviolated physical principles of the theory, then its matrix elements are
uniquely determined in terms of the fundamental parameters of the theory. This
method is designed to be applied to QCD, but for simplicity, we illustrate our
method by computing and analyzing second- and third-order matrix elements of
the Hamiltonian in massless phi-cubed theory in six dimensions.Comment: 47 pages, 6 figures; improved referencing, minor presentation change
Perbaikan Tegangan Pada Penyulang SMU 5 Dengan Pemasangan Kapasitor Shunt
Seiring dengan pertumbuhan beban yang umumnya merupakan beban induktif karena makin bertambahnya kebutuhan akan tenaga listik maka permasalahan yang mungkin timbul dari pertumbuhan beban- beban ini adalah tingginya jatuh tegangan. Altematif yang dapat dilakukan untuk memperbaiki profil tegangan tersebut adalah dengan melakukan kompensasi daya reaktif yaitu dengan memasang kapasitor shunt. Penelitian ini bertujuan untuk menentukan lokasi pemasangan dan kapasilas kapasitor shunt untuk memperbaiki profil tegangan penyulang Semanu 5 dengan menggunakan aplikasi program Electrical Transient Analizer Program (ETAP) PowerStation 4.0.0.
Dari hasil perbaikan profil tegangan yang telah dilakukan pada penyulang Semanu 5 dengan kapasitor shunt, yaitu switch capasitor dengan nilai 1800 kVAR dan sebuah fIxed capasitor dengan nilai 1800 kVAR kenaikan tegangan pada bus yang memiliki tegangan paling rendah mencapai 19,939 kV dari tegangan awal 18,156 kV saat WBP dan kenaikan tegangan pada bus yang memiliki tegangan paling rendah mencapai 20,316 kV dari tegangan awal 19,436 KV saat LWBP
Note on restoring manifest rotational symmetry in hyperfine and fine structure in light-front QED
We study the part of the renormalized, cutoff QED light-front Hamiltonian
that does not change particle number. The Hamiltonian contains interactions
that must be treated in second-order bound state perturbation theory to obtain
hyperfine structure. We show that a simple unitary transformation leads
directly to the familiar Breit-Fermi spin-spin and tensor interactions, which
can be treated in degenerate first-order bound-state perturbation theory, thus
simplifying analytic light-front QED calculations. To the order in momenta we
need to consider, this transformation is equivalent to a Melosh rotation. We
also study how the similarity transformation affects spin-orbit interactions.Comment: 17 pages, latex fil
Quarkonia in Hamiltonian Light-Front QCD
A constituent parton picture of hadrons with logarithmic confinement
naturally arises in weak coupling light-front QCD. Confinement provides a mass
gap that allows the constituent picture to emerge. The effective renormalized
Hamiltonian is computed to , and used to study charmonium and
bottomonium. Radial and angular excitations can be used to fix the coupling
, the quark mass , and the cutoff . The resultant hyperfine
structure is very close to experiment.Comment: 9 pages, 1 latex figure included in the text. Published version (much
more reader-friendly); corrected error in self-energ
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