695 research outputs found
A ``Gaussian'' Approach to Computing Supersymmetric Effective Actions
For nonsupersymmetric theories, the one-loop effective action can be computed
via zeta function regularization in terms of the functional trace of the heat
kernel associated with the operator which appears in the quadratic part of the
action. A method is developed for computing this functional trace by exploiting
its similarity to a Gaussian integral. The procedure is extended to superspace,
where it is used to compute the low energy effective action obtained by
integrating out massive scalar supermultiplets in the presence of a
supersymmetric Yang-Mills background.Comment: 17 pages, Latex, elsar
Peculiarities of the stochastic motion in antiferromagnetic nanoparticles
Antiferromagnetic (AFM) materials are widely used in spintronic devices as
passive elements (for stabilization of ferromangetic layers) and as active
elements (for information coding). In both cases switching between the
different AFM states depends in a great extent from the environmental noise. In
the present paper we derive the stochastic Langevin equations for an AFM vector
and corresponding Fokker-Planck equation for distribution function in the phase
space of generalised coordinate and momentum. Thermal noise is modeled by a
random delta-correlated magnetic field that interacts with the dynamic
magnetisation of AFM particle. We analyse in details a particular case of the
collinear compensated AFM in the presence of spin-polarised current. The energy
distribution function for normal modes in the vicinity of two equilibrium
states (static and stationary) in sub- and super-critical regimes is found. It
is shown that the noise-induced dynamics of AFM vector has pecuilarities
compared to that of magnetisation vector in ferromagnets.Comment: Submitted to EPJ ST, presented at the 4-th Conference on Statistical
Physics, Lviv, Ukraine, 201
Effects of unidirectional flow shear stresses on the formation, fractal microstructure and rigidity of incipient whole blood clots and fibrin gels
Incipient clot formation in whole blood and fibrin gels was studied by the rheometric techniques of controlled stress
parallel superposition (CSPS) and small amplitude oscillatory shear (SAOS). The effects of unidirectional shear stress on incipient
clot microstructure, formation kinetics and elasticity are reported in terms of the fractal dimension (df ) of the fibrin network,
the gel network formation time (TGP ) and the shear elastic modulus, respectively. The results of this first haemorheological
application of CSPS reveal the marked sensitivity of incipient clot microstructure to physiologically relevant levels of shear
stress, these being an order of magnitude lower than have previously been studied by SAOS. CSPS tests revealed that exposure
of forming clots to increasing levels of shear stress produces a corresponding elevation in df , consistent with the formation of
tighter, more compact clot microstructures under unidirectional flow. A corresponding increase in shear elasticity was recorded.
The scaling relationship established between shear elasticity and df for fibrin clots and whole blood confirms the fibrin network
as the dominant microstructural component of the incipient clot in terms of its response to imposed stress. Supplementary studies
of fibrin clot formation by rheometry and microscopy revealed the substantial additional network mass required to increase df
and provide evidence to support the hypothesis that microstructural changes in blood clotted under unidirectional shear may be
attributed to flow enhanced thrombin generation and activation. CSPS also identified a threshold value of unidirectional shear
stress above which no incipient clot formation could be detected. CSPS was shown to be a valuable haemorheological tool for
the study of the effects of physiological and pathological levels of shear on clot properties
Negative Kaons in Dense Baryonic Matter
Kaon polarization operator in dense baryonic matter of arbitrary isotopic
composition is calculated including s- and p-wave kaon-baryon interactions. The
regular part of the polarization operator is extracted from the realistic
kaon-nucleon interaction based on the chiral and 1/N_c expansion. Contributions
of the Lambda(1116), Sigma(1195), Sigma*(1385) resonances are taken explicitly
into account in the pole and regular terms with inclusion of mean-field
potentials. The baryon-baryon correlations are incorporated and fluctuation
contributions are estimated. Results are applied for K- in neutron star matter.
Within our model a second-order phase transition to the s-wave K- condensate
state occurs at rho_c \gsim 4 \rho_0 once the baryon-baryon correlations are
included. We show that the second-order phase transition to the p-wave
condensate state may occur at densities in
dependence on the parameter choice. We demonstrate that a first-order phase
transition to a proton-enriched (approximately isospin-symmetric) nucleon
matter with a p-wave K- condensate can occur at smaller densities, \rho\lsim 2
\rho_0. The transition is accompanied by the suppression of hyperon
concentrations.Comment: 41 pages, 24 figures, revtex4 styl
Comparing ‘apples with apples’: professional accounting practices in university classroom discourse
How are professional accounting practices represented in university classroom discourse and what are the implications of this for theory and practice in professional learning? Professional accounting practices order the world, and are also ordered. In reducing the complexities of social activity to abstract meanings that render it measurable, diverse and complex structures can be compared ‘apples with apples’. This study investigates the relocalization of professional accounting practices in university classroom discourse, working with tools from Legitimation Code Theory, systemic functional linguistics and critical discourse analysis. Findings draw on digital recordings of seminars presented by three lecturers in different subjects of a Master of Accounting program in an Australian metropolitan university. The analysis examines movements between context-independent and more context-dependent meanings in classroom discourse that mark shifts in emphasis from accounting as a system of representation, to accounting as interpersonal exchange. It considers two sets of social relations at play in the professional classroom: those between lecturers and students, and those within professional practice that are relocalized in classroom discourse. The framework developed in this study complements current research within the sociology of education. Discussion connects the analysis with recent explorations of knowledge practices in education within Legitimation Code Theory. It draws on foundational principles of a systemic functional model of language, considering the basis of professional practice and professional learning in interpersonal exchange. Conclusions are oriented towards theory and practice in professional learning, recognizing professional educators as agents of change and mediators of ways of thinking and acting in their field that are potentially transformative
Scalar Mesons in a Chiral Quark Model with Glueball
Ground-state scalar isoscalar mesons and a scalar glueball are described in a
U(3)xU(3) chiral quark model of the Nambu--Jona-Lasinio (NJL) type with 't
Hooft interaction. The latter interaction produces singlet-octet mixing in the
scalar and pseudoscalar sectors. The glueball is introduced into the effective
meson Lagrangian as a dilaton on the base of scale invariance. The mixing of
the glueball with scalar isoscalar quarkonia and amplitudes of their decays
into two pseudoscalar mesons are shown to be proportional to current quark
masses, vanishing in the chiral limit. Mass spectra of the scalar mesons and
the glueball and their main modes of strong decay are described.Comment: 10 pages, LaTeX text, requires svjour.cls and svepj.cl
Search for Exotic Mesons in pi- P Interactions at 18 GeV/c
The recent search for non mesons in interactions at
Brookhaven National Laboratory is summarized. Many final states such as , , , , , ,
which are favored decay modes of exotics, are under investigation.Comment: 9 pages, PostScript, Presented at the International School of Nuclear
Physics, Erice, Sicily, Italy, September 199
Confirmation of a pi_1^0 Exotic Meson in the \eta \pi^0 System
The exclusive reaction , at 18 GeV has been studied with a partial wave analysis on a sample
of 23~492 events from BNL experiment E852. A mass-dependent fit
is consistent with a resonant hypothesis for the wave, thus providing
evidence for a neutral exotic meson with , a mass of MeV, and a width of MeV. New
interpretations of the meson exotics in neutral system observed in
E852 and Crystal Barrel experiments are discussed.Comment: p3, rewording the paragraph (at the bottom) about the phase
variations. p4, rewording paragrath "The second method ..." . p4, at the
bottom of paragrath "The third method ..." added consistent with the results
of methods 1 and 2
Exotic Meson Production in the System observed in the Reaction at 18 GeV/c
This letter reports results from the partial wave analysis of the
final state in collisions at 18GeV/c.
Strong evidence is observed for production of two mesons with exotic quantum
numbers of spin, parity and charge conjugation, in the decay
channel . The mass MeV/c^2 and
width MeV/c^2 of the first state are consistent
with the parameters of the previously observed . The second
resonance with mass MeV/c^2 and width MeV/c^2 agrees very well with predictions from theoretical
models. In addition, the presence of is confirmed with mass MeV/c^2 and width MeV/c^2
and a new state, , is observed with mass
MeV/c^2 and width MeV/c^2. The decay properties of
these last two states are consistent with flux tube model predictions for
hybrid mesons with non-exotic quantum numbers
Study of KS KL Coupled Decays and KL -Be Interactions with the CMD-2 Detector at VEPP-2M Collider
The integrated luminosity about 4000 inverse nanobarn of around phi meson
mass ( 5 millions of phi mesons) has been collected with the CMD-2 detector at
the VEPP-2M collider. A latest analysis of the KS KL coupled decays based on 30
% of available data is presented in this paper.
The KS KL pairs from phi meson decays were reconstructed in the drift chamber
when both kaons decayed into two charged particles. From a sample of 1423
coupled decays a selection of candidates to the CP violating KL into pi+ pi-
decay was performed. CP violating decays were not identified because of the
domination of events with a KL regenerating at the Be beam pipe into KS and a
background from KL semileptonic decays.
The regeneration cross section of 110 MeV/c KL mesons was found to be 53 +-
17 mb in agreement with theoretical expectations. The angular distribution of
KS mesons after regeneration and the total cross section of KL for Be have been
measured.Comment: 14 pages, 8 figure
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