1,718 research outputs found
Majorana and the quasi-stationary states in Nuclear Physics
A complete theoretical model describing artificial disintegration of nuclei
by bombardment with alpha-particles, developed by Majorana as early as in 1930,
is discussed in detail alongside the basic experimental evidences that
motivated it. By following the quantum dynamics of a state resulting from the
superposition of a discrete state with a continuum one, whose interaction is
described by a given potential term, Majorana obtained (among the other
predictions) the explicit expression for the integrated cross section of the
nuclear process, which is the direct measurable quantity of interest in the
experiments. Though this is the first application of the concept of
quasi-stationary states to a Nuclear Physics problem, it seems also that the
unpublished Majorana's work anticipates by several years the related seminal
paper by Fano on Atomic Physics.Comment: latex, amsart, 13 page
Time-Averaged Adiabatic Potentials: Versatile traps and waveguides for ultracold quantum gases
We demonstrate a novel class of trapping potentials, time-averaged adiabatic
potentials (TAAP) which allows the generation of a large variety of traps and
waveguides for ultracold atoms. Multiple traps can be coupled through
controllable tunneling barriers or merged altogether. We present analytical
expressions for pancake-, cigar-, and ring- shaped traps. The ring-geometry is
of particular interest for guided matter-wave interferometry as it provides a
perfectly smooth waveguide of controllable diameter, and thus a tunable
sensitivity of the interferometer.Comment: 5 pages, 3 figure
Prospects for observing and localizing gravitational-wave transients with Advanced LIGO, Advanced Virgo and KAGRA
We present our current best estimate of the plausible observing scenarios for the
Advanced LIGO, Advanced Virgo and KAGRA gravitational-wave detectors over
the next several years, with the intention of providing information to facilitate
planning for multi-messenger astronomy with gravitational waves. We estimate the
sensitivity of the network to transient gravitational-wave signals for the third (O3),
fourth (O4) and fifth observing (O5) runs, including the planned upgrades of the
Advanced LIGO and Advanced Virgo detectors. We study the capability of the
network to determine the sky location of the source for gravitational-wave signals
from the inspiral of binary systems of compact objects, that is binary neutron star,
neutron star–black hole, and binary black hole systems. The ability to localize the
sources is given as a sky-area probability, luminosity distance, and comoving
volume. The median sky localization area (90% credible region) is expected to be a
few hundreds of square degrees for all types of binary systems during O3 with the
Advanced LIGO and Virgo (HLV) network. The median sky localization area will
improve to a few tens of square degrees during O4 with the Advanced LIGO, Virgo,
and KAGRA (HLVK) network. During O3, the median localization volume (90%
credible region) is expected to be on the order of 105; 106; 107 Mpc3 for binary
neutron star, neutron star–black hole, and binary black hole systems, respectively.
The localization volume in O4 is expected to be about a factor two smaller than in
O3. We predict a detection count of 1Ăľ121 (10Ăľ5210) for binary neutron star mergers, of
0þ190 (1þ911 ) for neutron star–black hole mergers, and 17þ2211(79þ89
44) for binary black hole mergers in a one-calendar-year observing run of the HLV network during O3
(HLVK network during O4). We evaluate sensitivity and localization expectations
for unmodeled signal searches, including the search for intermediate mass black
hole binary mergers
Distributions of money in model markets of economy
We study the distributions of money in a simple closed economic system for
different types of monetary transactions. We know that for arbitrary and random
sharing but locally conserving money transactions, the money distribution goes
to the Gibb's distribution of statistical mechanics. We then consider the
effects of savings, etc. and see how the distribution changes. We also propose
a new model where the agents invest equal amounts of money in each transaction.
We find that for short time-periods, the money distribution obeys a power-law
with an exponent very close to unity, and has an exponential tail; after a very
long time, this distribution collapses and the entire amount of money goes to a
tiny fraction of the population.Comment: 9 pages, 4 postscript figures. To appear in IJMPC 13 (2002
Inert states of spin-S systems
We present a simple but efficient geometrical method for determining the
inert states of spin-S systems. It can be used if the system is described by a
spin vector of a spin-S particle and its energy is invariant in spin rotations
and phase changes. Our method is applicable to an arbitrary S and it is based
on the representation of a pure spin state of a spin-S particle in terms of 2S
points on the surface of a sphere. We use this method to find candidates for
some of the ground states of spinor Bose-Einstein condensates.Comment: 4 pages, 2 figures, minor changes, references added, typos correcte
Majorana: from atomic and molecular, to nuclear physics
In the centennial of Ettore Majorana's birth (1906-1938?), we re-examine some
aspects of his fundamental scientific production in atomic and molecular
physics, including a not well known short communication. There, Majorana
critically discusses Fermi's solution of the celebrated Thomas-Fermi equation
for electron screening in atoms and positive ions. We argue that some of
Majorana's seminal contributions in molecular physics already prelude to the
idea of exchange interactions (or Heisenberg-Majorana forces) in his later
workson theoretical nuclear physics. In all his papers, he tended to emphasize
the symmetries at the basis of a physical problem, as well as the limitations,
rather than the advantages, of the approximations of the method employed.Comment: to appear in Found. Phy
Effect of aggregates and ITZ on visco-damaged response of concrete at the meso scale level
A deep knowledge on the behavior of concrete materials at the mesoscale level
requires, as a fundamental aspect, to characterize aggregates and specifically, their thermal
properties if fire hazards (e.g. spalling) are accounted for. The assessment of aggregates
performance (and, correspondingly, concrete materials made of aggregates, cement paste and
ITZ –interfacial transition zone-) is crucial for defining a realistic structural response as well
as damage scenarios. Particularly, it is assumed that concrete creep is associated to cement
paste only and that creep obeys to the B3 model proposed by Bazant and Baweja since it
shows good compatibility with experimental results and it is properly justified theoretically.
The fully coupled 3D F.E. code NEWCON3D has been adopted to perform meso-scale
analyses of concrete characterized by aggregates of different types and different thermal
conductivities. Damage maps allows for defining an appropriate concrete mixture for
responding to spalling and for characterizing the coupled behaviour of ITZ as well
A search for double beta decays of tin isotopes with enhanced sensitivity
A search for the various double beta decay modes of 124Sn and 112Sn has been
performed on 75 kg.days of data. New half-life limits for excited states in
124Sn have been obtained including a lower limit for the decay into the first
excited 2+ state of 124Te of T_half > 0.87e20 yrs (90% CL) and into the first
excited 0+ state of T_half > 1.08e20 yrs (90% CL). Ground state and excited
state transitions of 112Sn have also been experimentally explored. A limit for
the 2 neutrino double electron capture of T_half > 1.8e19 yrs (90% CL) is
obtained. The non-observation of de-excitation gammas from the 0+ at 1888.5keV
results in a lower half-life limit on the 0 neutrino double electron capture
decay of 112Sn of T_half > 0.8e19 yrs (90% CL), despite a possible resonant
enhancement of the decay rate due to degenerated states.Comment: 6 pages, 7 figures, updated analysis and tex
A simple test for hidden variables in spin-1 system
We resolve an old problem about the existence of hidden parameters in a
three-dimensional quantum system by constructing an appropriate Bell's type
inequality. This reveals a nonclassical nature of most spin- states. We
shortly discuss some physical implications and an underlying cause of this
nonclassical behavior, as well as a perspective of its experimental
verification.Comment: 4 pages, 1 figur
- …