8,244 research outputs found
A novel strong coupling expansion of the QCD Hamiltonian
Introducing an infinite spatial lattice with box length a, a systematic
expansion of the physical QCD Hamiltonian in \lambda = g^{-2/3} can be
obtained. The free part is the sum of the Hamiltonians of the quantum mechanics
of spatially constant fields for each box, and the interaction terms
proportional to \lambda^n contain n discretised spatial derivatives connecting
different boxes. As an example, the energy of the vacuum and the lowest scalar
glueball is calculated up to order \lambda^2 for the case of SU(2) Yang-Mills
theory.Comment: Talk given at the 6th International Workshop on "Critical Point and
Onset of Deconfinement (CPOD)", Dubna, Russia, 23-29 August 201
The Electroweak Vacuum Angle
We reveal a new source of CP-violation in the electroweak sector that is free
of any experimental bounds, and we highlight the possible implications for
baryogenesis.Comment: to appear in Physics Letters
Baryon Asymmetry, Dark Matter and Local Baryon Number
We propose a new mechanism to understand the relation between the baryon and
dark matter asymmetries in the universe in theories where the baryon number is
a local symmetry. In these scenarios the B-L asymmetry generated through a
mechanism such as leptogenesis is transferred to the dark matter and baryonic
sectors through sphalerons processes which conserve total baryon number. We
show that it is possible to have a consistent relation between the dark matter
relic density and the baryon asymmetry in the universe even if the baryon
number is broken at the low scale through the Higgs mechanism. We also discuss
the case where one uses the Stueckelberg mechanism to understand the
conservation of baryon number in nature.Comment: to appear in Physics Letters
Direction of movement effects under transformed visual/motor mappings
Performance in a discrete aiming task was compared under several transformed visual/motor mappings: rotations by 45, 90, 135, and 180 deg and reflections about the horizontal and the vertical midlines. Eight aiming targets were used, corresponding to eight directions of movement: up, down, right, left, up-right, down-left, up-left, and down-right. Direction of movements were characterized in terms of separable visual and motor components, and two kinds of direction of movement effects were considered. First, a direction of movement effect paralleling that seen in rapid aiming under the usual nontransformed mapping. Second, because rotations, but not reflections, are physically realizable 2-D transformations, a visual/motor control system which is sensitive to physical constraints should perform reflections, but not rotations, in a piecemeal fashion. Results supported the hypothesis that a motor factor having to do with complexity of limb movement accounts for differences in movement accuracy between right and left oblique directions. Direction of movement effects were more evident in reflections than in rotations, and were consistent with the hypothesis that the visual/motor-control system seeks a physically realizable 2-D rotation solution to reflections. Results also suggested that reversal of two orthogonal basis dimensions is far less difficult than reversing only one and leaving the other intact
Minimal Theory for Lepto-Baryons
We investigate the simplest models where baryon and lepton numbers are
defined as local symmetries spontaneously broken at the low scale and discuss
the implications for cosmology. We define the simplest anomaly-free theory for
spontaneous baryon and lepton number violation which predicts the existence of
lepto-baryons. In this context we study the new sphaleron condition on the
chemical potentials and show the relation between the present baryon asymmetry
and the B-L asymmetry generated in the early universe. The properties of the
cold dark matter candidate for which stability is a natural consequence from
symmetry breaking are briefly discussed.Comment: to appear in Physics Letters
Emergence of helical edge conduction in graphene at the \nu=0 quantum Hall state
The conductance of graphene subject to a strong, tilted magnetic field
exhibits a dramatic change from insulating to conducting behavior with
tilt-angle, regarded as evidence for the transition from a canted
antiferromagnetic (CAF) to a ferromagnetic (FM) \nu=0 quantum Hall state. We
develop a theory for the electric transport in this system based on the
spin-charge connection, whereby the evolution in the nature of collective spin
excitations is reflected in the charge-carrying modes. To this end, we derive
an effective field theoretical description of the low-energy excitations,
associated with quantum fluctuations of the spin-valley domain wall
ground-state configuration which characterizes the two-dimensional (2D) system
with an edge. This analysis yields a model describing a one-dimensional charged
edge mode coupled to charge-neutral spin-wave excitations in the 2D bulk.
Focusing particularly on the FM phase, naively expected to exhibit perfect
conductance, we study a mechanism whereby the coupling to these bulk
excitations assists in generating back-scattering. Our theory yields the
conductance as a function of temperature and the Zeeman energy - the parameter
that tunes the transition between the FM and CAF phases - with behavior in
qualitative agreement with experiment.Comment: 16 pages, 1 figur
FutureFarm vision
This paper defines the first version of a vision of Future Farming project and also a knowledge management system used by European farms which will be designed and developed by the Future Farm project. An important part of the vision is a definition of external drivers and their influence on farm business in future. Paper is looking on a situation in three periods: short (2013), middle (2020) and long-term (2030). Our vision expects that the farming system will continuously converge to the situation of two types of farm: an industrial farm, which will guarantee both the food safety and the food security for European citizens, and multifunctional farms focused on environment protection. The recommendation proposes an architecture based on communication of interoperable services, so called Service Oriented Architecture (SOA), for easy integration of different levels and components of farm management.Farming, external drivers, future vision, knowledge management, SOA, Farm Management,
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