754 research outputs found
Gauging hadronic systems
We present a general method for incorporating the electromagnetic interaction
into descriptions of hadronic processes based on four-dimensional scattering
integral equations. The method involves the idea of gauging the scattering
equations themselves, and results in electromagnetic amplitudes where an
external photon is effectively coupled to every part of every strong
interaction diagram in the model. Current conservation is therefore implemented
in the theoretically correct fashion. To illustrate our gauging procedure we
apply it to the three-nucleon problem whose strong interactions are described
by standard three-body integral equations. In this way we obtain the
expressions needed to calculate all possible electromagnetic processes of the
three-nucleon system: the electromagnetic form factors of the three-body bound
state, pd->pd gamma, gamma 3He-> pd, gamma 3He-> ppn, etc. As the photon is
coupled everywhere in the strong interaction model, a unified description of
the NNN-gamma NNN system is obtained. An interesting aspect of our results is
the natural appearance of a subtraction term needed to avoid the overcounting
of diagrams.Comment: 6 pages, revtex, epsf, 1 postscript figure, talk at the 15th Int.
Conf. on Few-Body Problems in Physics, Groningen, Netherlands, 22-26 July
1997. To be published in Nucl. Phys.
Infinite series solutions of the symmetry equation for the dimensional continuous Toda chain
A sequence of solutions to the equation of symmetry for the continuous Toda
chain in dimensions is represented in explicit form. This fact leads to
the supposition that this equation is completely integrable.Comment: 9 pages, latex, no figure
Summary report on the geology of the proposed HS2 Route (3) in the Chesham and Amersham Constituency
This brief open-file report summarises the information available from the British Geological Survey (BGS), a component body of the Natural Environment Research Council (NERC), on the geology, hydrogeology and potential geological hazards of the proposed HS2 Route 3 within the Chesham and Amersham Constituency, and surrounding areas.
The report summarises the geology and hydrogeology of the district and highlights geological and hydrogeological considerations that may need further investigation along the route.
Further review and analysis of existing data and possible field investigation would be required to confirm details of the local geology.
The report was requested by Mrs Cheryl Gillan MP following a meeting with Dr Martin Smith, Head of Geology & Landscapes programme, on Monday 16th May 2011 at the offices of the Secretary of State for Wales in Whitehall
Vanishing magnetic mass in QED with a Chern-Simons term
We show that, at one loop, the magnetic mass vanishes at finite temperature
in QED in any dimension. In QED, even the zero temperature part can be
regularized to zero. We calculate the two loop contributions to the magnetic
mass in QED with a Chern-Simons term and show that it vanishes. We give a
simple proof which shows that the magnetic mass vanishes to all orders at
finite temperature in this theory. This proof also holds for QED in any
dimension.Comment: revtex, 7 pages, 5 figure
Hennessy-Milner Logic with Greatest Fixed Points as a Complete Behavioural Specification Theory
There are two fundamentally different approaches to specifying and verifying
properties of systems. The logical approach makes use of specifications given
as formulae of temporal or modal logics and relies on efficient model checking
algorithms; the behavioural approach exploits various equivalence or refinement
checking methods, provided the specifications are given in the same formalism
as implementations.
In this paper we provide translations between the logical formalism of
Hennessy-Milner logic with greatest fixed points and the behavioural formalism
of disjunctive modal transition systems. We also introduce a new operation of
quotient for the above equivalent formalisms, which is adjoint to structural
composition and allows synthesis of missing specifications from partial
implementations. This is a substantial generalisation of the quotient for
deterministic modal transition systems defined in earlier papers
Abelian Toda field theories on the noncommutative plane
Generalizations of GL(n) abelian Toda and abelian affine
Toda field theories to the noncommutative plane are constructed. Our proposal
relies on the noncommutative extension of a zero-curvature condition satisfied
by algebra-valued gauge potentials dependent on the fields. This condition can
be expressed as noncommutative Leznov-Saveliev equations which make possible to
define the noncommutative generalizations as systems of second order
differential equations, with an infinite chain of conserved currents. The
actions corresponding to these field theories are also provided. The special
cases of GL(2) Liouville and sinh/sine-Gordon are
explicitly studied. It is also shown that from the noncommutative
(anti-)self-dual Yang-Mills equations in four dimensions it is possible to
obtain by dimensional reduction the equations of motion of the two-dimensional
models constructed. This fact supports the validity of the noncommutative
version of the Ward conjecture. The relation of our proposal to previous
versions of some specific Toda field theories reported in the literature is
presented as well.Comment: v3 30 pages, changes in the text, new sections included and
references adde
Forming Planetesimals in Solar and Extrasolar Nebulae
Planets are built from planetesimals: solids larger than a kilometer which
grow by colliding pairwise. Planetesimals themselves are unlikely to form by
two-body collisions; sub-km objects have gravitational fields individually too
weak, and electrostatic attraction is too feeble for growth beyond a few cm. We
review the possibility that planetesimals form when self-gravity brings
together vast ensembles of small particles. Even when self-gravity is weak,
aerodynamic processes can accumulate solids relative to gas, paving the way for
gravitational collapse. Particles pile up as they drift radially inward. Gas
turbulence stirs particles, but can also seed collapse by clumping them. While
the feedback of solids on gas triggers vertical shear instabilities that
obstruct self-gravity, this same feedback triggers streaming instabilities that
strongly concentrate particles. Numerical simulations find that solids 10-100
cm in size gravitationally collapse in turbulent disks. We outline areas for
progress, including the possibility that still smaller objects self-gravitate.Comment: To appear in Annual Reviews. This review is intended to be both
current and pedagogical. Incorporates suggestions from the community; further
comments welcome. v2: Single-space
A look at the consumption behaviours along Ghana’s slave routes.
This study examines the consumption behaviours of four types of visitors to sites associated with the Transatlantic Slave Trade in Ghana. A questionnaire was used to elicit information regarding sites they intended or actually visited, perceived differences regarding site experiences and impressions of the heritage product itself. The results show that visitors were highly selective in their consumption patterns, although the sites in the country’s south were the major attractions and generators for all purposes. There is evidence that trip motive and connection to slavery influence consumption behaviour, as some visitors are willing to invest effort, expense and time to consume truly unique learning experiences. The findings were interpreted as evidence that site managers may need to design strategies using visitor profile and consumption patterns to deliver a coordinated and integrated appeal to the target visitor group
Pion, kaon, proton and anti-proton transverse momentum distributions from p+p and d+Au collisions at GeV
Identified mid-rapidity particle spectra of , , and
from 200 GeV p+p and d+Au collisions are reported. A
time-of-flight detector based on multi-gap resistive plate chamber technology
is used for particle identification. The particle-species dependence of the
Cronin effect is observed to be significantly smaller than that at lower
energies. The ratio of the nuclear modification factor () between
protons and charged hadrons () in the transverse momentum
range GeV/c is measured to be
(stat)(syst) in minimum-bias collisions and shows little
centrality dependence. The yield ratio of in minimum-bias d+Au
collisions is found to be a factor of 2 lower than that in Au+Au collisions,
indicating that the Cronin effect alone is not enough to account for the
relative baryon enhancement observed in heavy ion collisions at RHIC.Comment: 6 pages, 4 figures, 1 table. We extended the pion spectra from
transverse momentum 1.8 GeV/c to 3. GeV/
Lorentz breaking Effective Field Theory and observational tests
Analogue models of gravity have provided an experimentally realizable test
field for our ideas on quantum field theory in curved spacetimes but they have
also inspired the investigation of possible departures from exact Lorentz
invariance at microscopic scales. In this role they have joined, and sometime
anticipated, several quantum gravity models characterized by Lorentz breaking
phenomenology. A crucial difference between these speculations and other ones
associated to quantum gravity scenarios, is the possibility to carry out
observational and experimental tests which have nowadays led to a broad range
of constraints on departures from Lorentz invariance. We shall review here the
effective field theory approach to Lorentz breaking in the matter sector,
present the constraints provided by the available observations and finally
discuss the implications of the persisting uncertainty on the composition of
the ultra high energy cosmic rays for the constraints on the higher order,
analogue gravity inspired, Lorentz violations.Comment: 47 pages, 4 figures. Lecture Notes for the IX SIGRAV School on
"Analogue Gravity", Como (Italy), May 2011. V.3. Typo corrected, references
adde
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