5,475 research outputs found
Work and energy in inertial and non inertial reference frames
It is usual in introductory courses of mechanics to develop the work and
energy formalism from Newton's laws. On the other hand, literature analyzes the
way in which forces transform under a change of reference frame.
Notwithstanding, no analogous study is done for the way in which work and
energy transform under those changes of reference frames. We analyze the
behavior of energy and work under such transformations and show explicitly the
expected invariance of the formalism under Galilean transformations for one
particle and a system of particles. The case of non inertial systems is also
analyzed and the fictitious works are characterized. In particular, we show
that the total fictitious work in the center of mass system vanishes even if
the center of mass defines a non inertial frame. Finally, some subtleties that
arise from the formalism are illustrated by examples.Comment: 4 pages, 2 figures. LaTeX2e. Part of the approach has been changed
but results are unaltered. Version to appear im American Journal of Physic
Hyperonic crystallization in hadronic matter
Published in Hadrons, Nuclei and Applications, World Scientific, Singapore,
Proc.of the Conference Bologna2000. Structure of the Nucleus at the Dawn of the
Century, G. Bonsignori, M. Bruno, A. Ventura, D. Vretenar Editors, pag. 319.Comment: 4 pages, 2figure
Friedel Oscillations in Relativistic Nuclear Matter
We calculate the low-momentum N-N effective potential obtained in the OBE
approximation, inside a nuclear plasma at finite temperature, as described by
the relativistic - model. We analyze the screening effects
on the attractive part of the potential in the intermediate range as density or
temperature increase. In the long range the potential shows Friedel-like
oscillations instead of the usual exponential damping. These oscillations arise
from the sharp edge of the Fermi surface and should be encountered in any
realistic model of nuclear matter.Comment: 11 pages in preprint format, typeset using REVTEX, 3 included figures
in tar, compressed, uuencoded forma
Optical detection of the radio supernova SN 2000ft in the circumnuclear region of the luminous infrared galaxy NGC 7469
SN 2000ft is detected in two independent Planetary Camera images (F547W and
F814W) taken May 13, 2000, about two months before the predicted date of the
explosion (July 19, 2000), based on the analysis of its radio light evolution
by Alberdi and collaborators. The apparent optical magnitudes and red color of
SN 2000ft indicate that it is observed through an extinction of at least A=
3.0 magnitudes. The extinction corrected lower limit to the absolute visual
magnitude (M 18.0), identifies SN 2000ft as a luminous supernova
in the optical, as other luminous radio supernovae before. SN 2000ft exploded
in a region located at only 0.1 arcsec (i.e. 34 +/- 3 pc) west of a faint
cluster (C24). No parent cluster is identified within the detection limits of
the HST short exposures. The unambiguous detection of SN 2000ft in the visual
shows that multi-epoch sub-arcsecond (FWHM less than 0.1 arcsec) optical
imaging is also a valid tool that should be explored further to detect
supernovae in the dusty (circum)nuclear regions of (U)LIRGs
Nucleon-nucleon effective potential in dense matter including rho-meson exchange
We obtain the RPA summed one-meson exchange potential between nucleons in symmetric nuclear matter at zero temperature, from a model which includes rho, sigma, omega and pi mesons. The behavior of rho mesons inside the medium is first discussed using different schemes to extract a finite contribution from the vacuum polarization. These schemes give qualitatively different results for the in-medium rho mass. The results are discussed in connection with the nourenormalizability of the model. We next study the modified potential as density increases. In the intermediate-distance range, it is qualitatively modified by matter and vacuum effects. In the long-distance range (r > 2 fm), one observes the presence of oscillations, which are not present in free space. Features on this distance range arc insensitive to the renormalization scheme
Electrostatic internal energy using the method of images
For several configurations of charges in the presence of conductors, the
method of images permits us to obtain some observables associated with such a
configuration by replacing the conductors with some image charges. However,
simple inspection shows that the potential energy associated with both systems
does not coincide. Nevertheless, it can be shown that for a system of a
grounded or neutral conductor and a distribution of charges outside, the
external potential energy associated with the real charge distribution embedded
in the field generated by the set of image charges is twice the value of the
internal potential energy associated with the original system. This assertion
is valid for any size and shape of the conductor, and regardless of the
configuration of images required. In addition, even in the case in which the
conductor is not grounded nor neutral, it is still possible to calculate the
internal potential energy of the original configuration through the method of
images. These results show that the method of images could also be useful for
calculations of the internal potential energy of the original system.Comment: 5 pages, 3 figures. New discussions added. Minor change
Thermodynamic analysis of black hole solutions in gravitating nonlinear electrodynamics
We perform a general study of the thermodynamic properties of static
electrically charged black hole solutions of nonlinear electrodynamics
minimally coupled to gravitation in three space dimensions. The Lagrangian
densities governing the dynamics of these models in flat space are defined as
arbitrary functions of the gauge field invariants, constrained by some
requirements for physical admissibility. The exhaustive classification of these
theories in flat space, in terms of the behaviour of the Lagrangian densities
in vacuum and on the boundary of their domain of definition, defines twelve
families of admissible models. When these models are coupled to gravity, the
flat space classification leads to a complete characterization of the
associated sets of gravitating electrostatic spherically symmetric solutions by
their central and asymptotic behaviours. We focus on nine of these families,
which support asymptotically Schwarzschild-like black hole configurations, for
which the thermodynamic analysis is possible and pertinent. In this way, the
thermodynamic laws are extended to the sets of black hole solutions of these
families, for which the generic behaviours of the relevant state variables are
classified and thoroughly analyzed in terms of the aforementioned boundary
properties of the Lagrangians. Moreover, we find universal scaling laws (which
hold and are the same for all the black hole solutions of models belonging to
any of the nine families) running the thermodynamic variables with the electric
charge and the horizon radius. These scale transformations form a one-parameter
multiplicative group, leading to universal "renormalization group"-like
first-order differential equations. The beams of characteristics of these
equations generate the full set of black hole states associated to any of these
gravitating nonlinear electrodynamics...Comment: 51 single column pages, 19 postscript figures, 2 tables, GRG tex
style; minor corrections added; final version appearing in General Relativity
and Gravitatio
Solutions of the dispersion equation in the region of overlapping of zero-sound and particle-hole modes
In this paper the solutions of the zero-sound dispersion equation in the
random phase approximation (RPA) are considered. The calculation of the damped
zero-sound modes \omega_s(k) (complex frequency of excitation) in the nuclear
matter is presented. The method is based on the analytical structure of the
polarization operators \Pi(\omega,k). The solutions of two dispersion equations
with \Pi(\omega,k) and with Re(\Pi(\omega,k)) are compared. It is shown that in
the first case we obtain one-valued smooth solutions without "thumb-like"
forms. Considering the giant resonances in the nuclei as zero-sound excitations
we compare the experimental energy and escape width of the giant dipole
resonance (GDR) in the nucleus A with \omega_s(k) taken at a definite wave
vector k=k_A.Comment: 14 pages, 5 figures; revised versio
Work and energy in rotating systems
Literature analyzes the way in which Newton's second law can be used when
non-inertial rotating systems are used. However, the treatment of the work and
energy theorem in rotating systems is not considered in textbooks. In this
paper, we show that the work and energy theorem can still be applied to a
closed system of particles in a rotating system, as long as the work of
fictitious forces is properly included in the formalism. The coriolis force
does not contribute to the work coming from fictitious forces. It worths
remarking that real forces that do not do work in an inertial reference frame
can do work in the rotating reference frame and viceversa. The combined effects
of acceleration of the origin and rotation of the non-inertial system are also
studied.Comment: 6 pages, 3 figures, LaTeX2
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