3,002 research outputs found
Two-level interacting boson models beyond the mean field
The phase diagram of two-level boson Hamiltonians, including the Interacting
Boson Model (IBM), is studied beyond the standard mean field approximation
using the Holstein-Primakoff mapping. The limitations of the usual intrinsic
state (mean field) formalism concerning finite-size effects are pointed out.
The analytic results are compared to numerics obtained from exact
diagonalizations. Excitation energies and occupation numbers are studied in
different model space regions (Casten triangle for IBM) and especially at the
critical points.Comment: 14 pages, 13 figure
Finite-size scaling exponents in the interacting boson model
We investigate the finite-size scaling exponents for the critical point at
the shape phase transition from U(5) (spherical) to O(6) (deformed
-unstable) dynamical symmetries of the Interacting Boson Model, making
use of the Holstein-Primakoff boson expansion and the continuous unitary
transformation technique. We compute exactly the leading order correction to
the ground state energy, the gap, the expectation value of the -boson number
in the ground state and the transition probability from the ground state
to the first excited state, and determine the corresponding finite-size scaling
exponents.Comment: 4 pages, 3 figures, published versio
Assessment of lot shape in business park design
Planning and developing a business park is a complex task, whichdemands integration across various
fields of design and knowledge. The first choice to be made in the design process is relate to the zoning process
and the definition of the lot layout and landscape. These first decisions will constrain all subsequent decisions
concerning utilities, facilities and amenities. For this reason, the assessment of those issues is crucial for the
perception of the overall quality of the business park design. The main goal of this work is to present a simple
indicator which can assess the lot shape in order to optimize the building form and costs, the use of its open
areas, the layout and the economic spacing of roads and the service routes. The indicator lot shape evaluatesthe
performance of the lot design solutions according to the concept of compactness
Air quality in the North of Portugal.
Air pollution in urban areas is a major topic of concern in many large cities. In Portugal, a monitoring
network measures relevant pollutants for zones and agglomerations. The measurements of two zones and four
agglomerations located in the North of Portugal were used to diagnose the pollution level and the relative air
quality. It was found that, despite the need for densification of the network of monitoring stations, ozone (O3)
and particulate matter (PM10) reach significant levels in a number of days during the year. Some
recommendations are made regarding the inclusion of planning and mitigation actions in the Regional and
Municipal Master Plan
Relationship between X(5)-models and the interacting boson model
The connections between the X(5)-models (the original X(5) using an infinite
square well, X(5)-, X(5)-, X(5)-, and
X(5)-), based on particular solutions of the geometrical Bohr
Hamiltonian with harmonic potential in the degree of freedom, and the
interacting boson model (IBM) are explored. This work is the natural extension
of the work presented in [1] for the E(5)-models. For that purpose, a quite
general one- and two-body IBM Hamiltonian is used and a numerical fit to the
different X(5)-models energies is performed, later on the obtained wave
functions are used to calculate B(E2) transition rates. It is shown that within
the IBM one can reproduce well the results for energies and B(E2) transition
rates obtained with all these X(5)-models, although the agreement is not so
impressive as for the E(5)-models. From the fitted IBM parameters the
corresponding energy surface can be extracted and it is obtained that,
surprisingly, only the X(5) case corresponds in the moderate large N limit to
an energy surface very close to the one expected for a critical point, while
the rest of models seat a little farther.Comment: Accepted in Physical Review
The potential at the U(5)-O(6) critical point of the Interacting Boson Model
Exact numerical results of the interacting boson model Hamiltonian along the
integrable line from U(5) to O(6) are obtained by diagonalization within boson
seniority subspaces. The matrix Hamiltonian reduces to a block tridiagonal form
which can be diagonalized for large number of bosons. We present results for
the low energy spectrum and the transition probabilities for systems up to
10000 bosons, which confirm that at the critical point the system is equally
well described by the Bohr Hamiltonian with a potential.Comment: To be published in PR
On the relation between models and the interacting boson model
The connections between the models (the original E(5) using an
infinite square well, , and ), based
on particular solutions of the geometrical Bohr Hamiltonian with
-unstable potentials, and the interacting boson model (IBM) are
explored. For that purpose, the general IBM Hamiltonian for the
transition line is used and a numerical fit to the different models
energies is performed, later on the obtained wavefunctions are used to
calculate B(E2) transition rates. It is shown that within the IBM one can
reproduce very well all these models. The agreement is the best for
and reduces when passing through ,
and E(5), where the worst agreement is obtained (although still very good for a
restricted set of lowest lying states). The fitted IBM Hamiltonians correspond
to energy surfaces close to those expected for the critical point. A phenomenon
similar to the quasidynamical symmetry is observed
Integrability of Lie systems and some of its applications in physics
The geometric theory of Lie systems will be used to establish integrability
conditions for several systems of differential equations, in particular Riccati
equations and Ermakov systems. Many different integrability criteria in the
literature will be analyzed from this new perspective and some applications in
physics will be given.Comment: 16 page
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