180 research outputs found
Scaling of variables and the relation between noncommutative parameters in Noncommutative Quantum Mechanics
We consider Noncommutative Quantum Mechanics with phase space
noncommutativity. In particular, we show that a scaling of variables leaves the
noncommutative algebra invariant, so that only the self-consistent effective
parameters of the model are physically relevant. We also discuss the recently
proposed relation of direct proportionality between the noncommutative
parameters, showing that it has a limited applicability.Comment: Revtex4, 4 pages; version to match the published on
Astrophysical constraints on the confining models : the Field Correlator Method
We explore the relevance of confinement in quark matter models for the
possible quark core of neutron stars. For the quark phase, we adopt the
equation of state (EoS) derived with the Field Correlator Method, extended to
the zero temperature limit. For the hadronic phase, we use the microscopic
Brueckner-Hartree-Fock many-body theory. We find that the currently adopted
value of the gluon condensate , which gives
a critical temperature , produces maximum masses which
are only marginally consistent with the observational limit, while larger
masses are possible if the gluon condensate is increased.Comment: 7 pages, 5 figure
An alternative heavy Higgs mass limit
After commenting on the present value of the Higgs particle mass from
radiative corrections, we explore the phenomenological implications of an
alternative, non-perturbative renormalization of the scalar sector where the
mass of the Higgs particle does not represent a measure of observable
interactions at the Higgs mass scale. In this approach the Higgs particle could
be very heavy, even heavier than 1 TeV, and remain nevertheless a relatively
narrow resonance.Comment: 17 pages. Version accepted for publication in Journal of Physics
Nonuniform symmetry breaking in noncommutative theory
The spontaneous symmetry breaking in noncommutative theory
has been analyzed by using the formalism of the effective action for composite
operators in the Hartree-Fock approximation. It turns out that there is no
phase transition to a constant vacuum expectation of the field and the broken
phase corresponds to a nonuniform background. By considering the generated mass gap depends on the angles among
the momenta and and the noncommutativity parameter
. The order of the transition is not easily determinable in our
approximation.Comment: 18 pages, 4 figures, added reference
Autoimmune liver disease in a sicilian woman.
Autoimmune hepatitis (AIH) is a chronic liver disease characterized by clinical features analogue to viral and non-autoimmune
liver disorders, but with distinct sero-autoimmunologic properties. The disease results from a network of complex interactions
involving genetic predisposition, triggering factors, autoantigens and immunoregulatory system. Diagnosis of AIH relies on positive
autoantibodies determination and on liver core biopsy histological appearance. Corticosteroid and immunosuppressive drugs are generally useful in the treatment of disease. However, when inflammation cannot be controlled, progression from chronic hepatitis to cirrhosis is often observed and hepatocellular carcinoma may appear at the end stage. Here we reported a case of a woman, affected
with AIH. The patient presented features of chronic liver disease of neither viral nor alcoholic aetiology. Serum evidence of hypertraminasemia, hypergammaglobulinemia and specific autoantibodies were the leading points to final diagnosis, which was validated
by liver biopsy. The patient was, finally, successfully treated with steroids
The s-process weak component: uncertainties due to convective overshooting
Using a new s-nucleosynthesis code, coupled with the stellar evolution code
Star2003, we performed simulations to study the impact of the convection
treatment on the s-process during core He-burning of a 25 Msun star (ZAMS mass)
with an initial metallicity of Z=0.02. Particular attention was devoted to the
impact of the extent of overshooting on the s-process efficiency. The results
show enhancements of about a factor 2-3 in s-process efficiency (measured as
the average overproduction factor of the 6 s-only nuclear species with
) with overshooting parameter values in the range
0.01-0.035, compared to results obtained with the same model but without
overshooting. The impact of these results on the p-process model based on type
II supernovae is discussed.Comment: 7 pages, 4 figures, accepted for publication in Astronomy &
Astrophysic
Convective overshooting and production of s-nuclei in massive stars during their core He-burning phase
With the "post-processing" technique we explore the role of the convective
overshooting on the production of s-nuclei in stellar models of different
initial mass and metallicity (; ), considering a range of values for the parameter , which
determines the overall efficiency of convective overshooting.We find
enhancements in the production of s-nuclei until a factor (measured as
the average overproduction factor of the 6 s-only nuclear species with
) in all our models of different initial mass and
metallicity with in the range (i.e. models with
overshooting) compared to the production obtained with "no-overshooting" models
(i.e. models with the same initial mass and metallicity, but ).
Moreover the results indicate that the link between the overshooting parameter
and the s-process efficiency is essentially monotonic in all our models of
different initial mass and metallicity. Also evident is the higher s-process
efficiency when we progressively increase for a given f value both the mass of
the models from 15 M to 25 M and the Z value from 10 to
0.02. We also briefly discuss the possible consequences of these results for
some open questions linked to the s-process weak component efficiency, as well
as a "rule of thumb" to evaluate the impact of the convective overshooting on
the yields of a generation of stars.Comment: 12 pages, 6 figures, A&A accepted (corrected typos plus minor changes
in order to fulfill the guidelines for A&A manuscripts
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