1,377 research outputs found
Gravity in presence of fermions as a SU(2) gauge theory
The Hamiltonian formulation of the Holst action in presence of a massless
fermion field with a non-minimal Lagrangian is performed without any
restriction on the local Lorentz frame. It is outlined that the phase space
structure does not resemble that one of a background independent Lorentz gauge
theory, as some additional constraints are present. Proper phase space
coordinates are introduced, such that SU(2) connections can be defined and the
vanishing of conjugate momenta to boost variables is predicted. Finally, it is
demonstrated that for a particular value of the non-minimal parameter the
kinematics coincides with that one of a background independent SU(2) gauge
theory and the Immirzi parameter becomes the coupling constant of such an
interaction between fermions and the gravitational field.Comment: 5 pages, accepted for publication in Phys. Rev.
Chiral Bosons as solutions of the BV master equation 2D chiral gauge theories
We construct the chiral Wess-Zumino term as a solution for the
Batalin-Vilkovisky master equation for anomalous two-dimensional gauge
theories, working in an extended field-antifield space, where the gauge group
elements are introduced as additional degrees of freedom.
We analyze the Abelian and the non-Abelian cases, calculating in both cases
the BRST generator in order to show the physical equivalence between this
chiral solution for the master equation and the usual (non-chiral) one.Comment: 11 pages, TEX dialet, IF/UFRJ-94-
Fueled by a Fearful Leader: When, to What Extent and How Leader Fear of COVID-19 Promotes Employee Performance
The literature generally surmises that negative affective states of leaders are detrimental to leader effectiveness and work outcomes. Taking the opposite view, this study explores how the negative affective experiences of leaders related to COVID-19 may foster team commitment and employee performance. By integrating personality systems interaction theory, cognitive appraisal theory, and the literature on stress-based emotions, we develop a model that clarifies when, how, and to what extent leader fearful states related to COVID-19 drive employee performance. Using three-wave and multisource data from 579 employees and their leaders from 69 teams, we found that among leaders who exhibited higher levels of positive affectivity, leader fear of COVID-19 indirectly fostered employee performance via the mediating roles of leader promotion of team goals and team commitment. Moreover, these moderated indirect effects were strongest at moderate levels of leader fear of COVID-19. We discuss the theoretical and practical implications of these findings for research on leader affective states
Low-energy sector of 8-dimensional General Relativity: Electro-Weak model and neutrino mass
In a Kaluza-Klein space-time , we demonstrate that the
dimensional reduction of spinors provides a 4-field, whose associated SU(2)
gauge connections are geometrized. However, additional and gauge-violating
terms arise, but they are highly suppressed by a factor , which fixes
the amount of the spinor dependence on extra-coordinates. The application of
this framework to the Electro-Weak model is performed, thus giving a lower
bound for from the request of the electric charge conservation.
Moreover, we emphasize that also the Higgs sector can be reproduced, but
neutrino masses are predicted and the fine-tuning on the Higgs parameters can
be explained, too.Comment: 14 pages, 1 figure, to appear on Int. J. Mod. Phys.
Mean field and pairing properties in the crust of neutron stars
Properties of the matter in the inner crust of a neutron star are
investigated in a Hartree-Fock plus BCS approximation employing schematic
effective forces of the type of the Skyrme forces. Special attention is paid to
differences between a homogenous and inhomogeneous description of the matter
distribution. For that purpose self-consistent Hartree Fock calculations are
performed in a spherical Wigner-Seitz cell. The results are compared to
predictions of corresponding Thomas Fermi calculations. The influence of the
shell structure on the formation of pairing correlations in inhomogeneous
matter are discussed.Comment: 11 pages, 9 figure
Linear Two-Dimensional MHD of Accretion Disks: Crystalline structure and Nernst coefficient
We analyse the two-dimensional MHD configurations characterising the steady
state of the accretion disk on a highly magnetised neutron star. The model we
describe has a local character and represents the extension of the crystalline
structure outlined in Coppi (2005), dealing with a local model too, when a
specific accretion rate is taken into account. We limit our attention to the
linearised MHD formulation of the electromagnetic back-reaction characterising
the equilibrium, by fixing the structure of the radial, vertical and azimuthal
profiles. Since we deal with toroidal currents only, the consistency of the
model is ensured by the presence of a small collisional effect,
phenomenologically described by a non-zero constant Nernst coefficient (thermal
power of the plasma). Such an effect provides a proper balance of the electron
force equation via non zero temperature gradients, related directly to the
radial and vertical velocity components.
We show that the obtained profile has the typical oscillating feature of the
crystalline structure, reconciled with the presence of viscosity, associated to
the differential rotation of the disk, and with a net accretion rate. In fact,
we provide a direct relation between the electromagnetic reaction of the disk
and the (no longer zero) increasing of its mass per unit time. The radial
accretion component of the velocity results to be few orders of magnitude below
the equatorial sound velocity. Its oscillating-like character does not allow a
real matter in-fall to the central object (an effect to be searched into
non-linear MHD corrections), but it accounts for the out-coming of steady
fluxes, favourable to the ring-like morphology of the disk.Comment: 15 pages, 1 figure, accepted for publication on Modern Physics
Letters
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