253 research outputs found
Tri-hamiltonian vector fields, spectral curves and separation coordinates
We show that for a class of dynamical systems, Hamiltonian with respect to
three distinct Poisson brackets (P_0, P_1, P_2), separation coordinates are
provided by the common roots of a set of bivariate polynomials. These
polynomials, which generalise those considered by E. Sklyanin in his
algebro-geometric approach, are obtained from the knowledge of: (i) a common
Casimir function for the two Poisson pencils (P_1 - \lambda P_0) and (P_2 - \mu
P_0); (ii) a suitable set of vector fields, preserving P_0 but transversal to
its symplectic leaves. The frameworks is applied to Lax equations with spectral
parameter, for which not only it unifies the separation techniques of Sklyanin
and of Magri, but also provides a more efficient ``inverse'' procedure not
involving the extraction of roots.Comment: 49 pages Section on reduction revisite
The Role of Emotional Intelligence in Health Care Professionals Burnout
The purpose of this study is to explore the relationship between Emotional Intelligence (EI) and burnout in health care professionals. More specifically, this survey has the purpose of demonstrating the role of EI as a protective factor against the risk of burnout. Health professionals (doctors, nurses, and other caregivers) composed the sample. Data, collected during professional training, provided 148 employees. Major results of this survey underline the relationship between EI and burnout. As we expected, there is a negative and significant correlation between burnout and Emotional Intelligence. Moreover, burnout varies depending on length of service: burnout increases between 5 and 10 years of experience and decreases over 10 years. Indeed, burnout is differently expressed amongst healthcare professionals: more specifically, Psycho-physical exhaustion, Detriment of the relationships and Burnout (total score) has an impact on physician (doctors) more than other investigated health professionals. These findings seem to suggest the opportunity to improve Emotional Intelligence abilities through specific training programs, useful to promote the ability to cope with stress and to enrich the relationships in the workplace
Gauge Fixing in Higher Derivative Gravity
Linearized four-derivative gravity with a general gauge fixing term is
considered. By a Legendre transform and a suitable diagonalization procedure it
is cast into a second-order equivalent form where the nature of the physical
degrees of freedom, the gauge ghosts, the Weyl ghosts, and the intriguing
"third ghosts", characteristic to higher-derivative theories, is made explicit.
The symmetries of the theory and the structure of the compensating
Faddeev-Popov ghost sector exhibit non-trivial peculiarities.Comment: 21 pages, LaTe
Ostrogradski Formalism for Higher-Derivative Scalar Field Theories
We carry out the extension of the Ostrogradski method to relativistic field
theories. Higher-derivative Lagrangians reduce to second differential-order
with one explicit independent field for each degree of freedom. We consider a
higher-derivative relativistic theory of a scalar field and validate a powerful
order-reducing covariant procedure by a rigorous phase-space analysis. The
physical and ghost fields appear explicitly. Our results strongly support the
formal covariant methods used in higher-derivative gravity.Comment: 22 page
A new duality transformation for fourth-order gravity
We prove that for non-linear L = L(R), the Lagrangians L and \hat L give
conformally equivalent fourth-order field equations being dual to each other.
The proof represents a new application of the fact that the operator
is conformally invariant.Comment: 11 pages, LaTeX, no figures. Gen. Relat. Grav. in prin
Equivalence of black hole thermodynamics between a generalized theory of gravity and the Einstein theory
We analyze black hole thermodynamics in a generalized theory of gravity whose
Lagrangian is an arbitrary function of the metric, the Ricci tensor and a
scalar field. We can convert the theory into the Einstein frame via a
"Legendre" transformation or a conformal transformation. We calculate
thermodynamical variables both in the original frame and in the Einstein frame,
following the Iyer--Wald definition which satisfies the first law of
thermodynamics. We show that all thermodynamical variables defined in the
original frame are the same as those in the Einstein frame, if the spacetimes
in both frames are asymptotically flat, regular and possess event horizons with
non-zero temperatures. This result may be useful to study whether the second
law is still valid in the generalized theory of gravity.Comment: 14 pages, no figure
Constraining Newtonian stellar configurations in f(R) theories of gravity
We consider general metric theories of gravity by solving the field
equations in the presence of a spherical static mass distribution by analytical
perturbative means. Expanding the field equations systematically in \cO(G),
we solve the resulting set of equations and show that theories which
attempt to solve the dark energy problem very generally lead to
in the solar system. This excludes a large class of theories
as possible explanations of dark energy. We also present the first order
correction to and show that it cannot have a significant effect.Comment: 4 pages; v2: added references, modified abstract and introduction,
conclusions unchange
Higher-Derivative Boson Field Theories and Constrained Second-Order Theories
As an alternative to the covariant Ostrogradski method, we show that
higher-derivative relativistic Lagrangian field theories can be reduced to
second differential-order by writing them directly as covariant two-derivative
theories involving Lagrange multipliers and new fields. Despite the intrinsic
non-covariance of the Dirac's procedure used to deal with the constraints, the
explicit Lorentz invariance is recovered at the end. We develop this new
setting on the grounds of a simple scalar model and then its applications to
generalized electrodynamics and higher-derivative gravity are worked out. For a
wide class of field theories this method is better suited than Ostrogradski's
for a generalization to 2n-derivative theoriesComment: 31 pages, Plain Te
Local adsorption structure and bonding of porphine on Cu(111) before and after self-metalation
We have experimentally determined the lateral registry and geometric
structure of free-base porphine (2H-P) and copper-metalated porphine (Cu-P)
adsorbed on Cu(111), by means of energy-scanned photoelectron diffraction
(PhD), and compared the experimental results to density functional theory (DFT)
calculations that included van der Waals corrections within the
Tkatchenko-Scheffler approach. Both 2H-P and Cu-P adsorb with their center
above a surface bridge site. Consistency is obtained between the experimental
and DFT-predicted structural models, with a characteristic change in the
corrugation of the four N atoms of the molecule's macrocycle following
metalation. Interestingly, comparison with previously published data for cobalt
porphine adsorbed on the same surface evidences a distinct increase in the
average height of the N atoms above the surface through the series 2H-P, Cu-P,
cobalt porphine. Such an increase strikingly anti-correlates the DFT-predicted
adsorption strength, with 2H-P having the smallest adsorption height despite
the weakest calculated adsorption energy. In addition, our findings suggest
that for these macrocyclic compounds, substrate-to-molecule charge transfer and
adsorption strength may not be univocally correlated
Determinant-Gravity: Cosmological implications
We analyze the action as a possible alternative or addition to the Einstein gravity.
Choosing a particular form of we can restore the
Einstein gravity and, if , we obtain the cosmological constant
term. Taking and expanding the action in , we obtain as a leading term the Einstein Lagrangian with a cosmological
constant proportional to and a series of higher order operators. In
general case of non-vanishing and new cosmological
solutions for the Robertson-Walker metric are obtained.Comment: revtex format, 5 pages,8 figures,references adde
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