5,611 research outputs found
Does managing a SRI fund cost more? Evidence from the European financial market
open2Our aim is to provide evidence regarding managing costs differences comparing Socially Responsible Investing (SRI) funds with traditional ones, if any, and if these are influenced by the ethical rating of the fund. The methodology is based on a multiple linear regression model in a matched-pair sample of 309 European SRI and non-SRI funds managed by the same managing company and a comprehensive sample of 558 European SRI funds. Our main findings are on size, country, asset class, and ethical rating. Yet, the higher the ethical rating, the lower the TER, especially at the highest level of rating. If investors actively select higher ethically rated SRI funds, he or she will benefit from a lower cost charged by specialised asset managers. In investing in 'good', choose the best!openArrigoni, Stefania; Lanzavecchia, AlbertoArrigoni, Stefania; Lanzavecchia, Albert
Robust Motion Segmentation from Pairwise Matches
In this paper we address a classification problem that has not been
considered before, namely motion segmentation given pairwise matches only. Our
contribution to this unexplored task is a novel formulation of motion
segmentation as a two-step process. First, motion segmentation is performed on
image pairs independently. Secondly, we combine independent pairwise
segmentation results in a robust way into the final globally consistent
segmentation. Our approach is inspired by the success of averaging methods. We
demonstrate in simulated as well as in real experiments that our method is very
effective in reducing the errors in the pairwise motion segmentation and can
cope with large number of mismatches
On the correct continuum limit of the functional-integral representation for the four-slave-boson approach to the Hubbard model: Paramagnetic phase
The Hubbard model with finite on-site repulsion U is studied via the
functional-integral formulation of the four-slave-boson approach by Kotliar and
Ruckenstein. It is shown that a correct treatment of the continuum imaginary
time limit (which is required by the very definition of the functional
integral) modifies the free energy when fluctuation (1/N) corrections beyond
mean-field are considered. Our analysis requires us to suitably interpret the
Kotliar and Ruckenstein choice for the bosonic hopping operator and to abandon
the commonly used normal-ordering prescription, in order to obtain meaningful
fluctuation corrections. In this way we recover the exact solution at U=0 not
only at the mean-field level but also at the next order in 1/N. In addition, we
consider alternative choices for the bosonic hopping operator and test them
numerically for a simple two-site model for which the exact solution is readily
available for any U. We also discuss how the 1/N expansion can be formally
generalized to the four-slave-boson approach, and provide a simplified
prescription to obtain the additional terms in the free energy which result at
the order 1/N from the correct continuum limit.Comment: Changes: Printing problems (due to non-standard macros) have been
removed, 44 page
Spin-wave spectrum of a two-dimensional itinerant electron system: Analytic results for the incommensurate spiral phase in the strong-coupling limit
We study the zero-temperature spin fluctuations of a two-dimensional
itinerant-electron system with an incommensurate magnetic ground state
described by a single-band Hubbard Hamiltonian. We introduce the
(broken-symmetry) magnetic phase at the mean-field (Hartree-Fock) level through
a \emph{spiral spin configuration} with characteristic wave vector
\gmathbf{Q} different in general from the antiferromagnetic wave vector
\gmathbf{Q_{AF}}, and consider spin fluctuations over and above it within the
electronic random-phase (RPA) approximation. We obtain a \emph{closed} system
of equations for the generalized wave vector and frequency dependent
susceptibilities, which are equivalent to the ones reported recently by Brenig.
We obtain, in addition, analytic results for the spin-wave dispersion relation
in the strong-coupling limit of the Hubbard Hamiltonian and find that at finite
doping the spin-wave dispersion relation has a \emph{hybrid form} between that
associated with the (localized) Heisenberg model and that associated with the
(long-range) RKKY exchange interaction. We also find an instability of the
spin-wave spectrum in a finite region about the center of the Brillouin zone,
which signals a physical instability toward a different spin- or, possibly,
charge-ordered phase, as, for example, the stripe structures observed in the
high-Tc materials. We expect, however, on physical grounds that for wave
vectors external to this region the spin-wave spectrum that we have determined
should survive consideration of more sophisticated mean-field solutions.Comment: 30 pages, 4 eps figure
Competition Between Charge-Density Waves and Superconductivity in Striped Systems
Switching on interchain coupling in a system of one-dimensional strongly
interacting chains often leads to an ordered state. Quite generally, there is a
competition between an insulating charge-density-wave and a superconducting
state. In the case of repulsive interactions, charge-density wave usually wins
over superconductivity. Here, we show that a suitable modulation in the form of
a period 4 bond-centered stripe can reverse this balance even in the repulsive
case and produce a superconducting state with relatively high temperature.Comment: Proceedings of SCES 04, 2 page
On Computing the Translations Norm in the Epipolar Graph
This paper deals with the problem of recovering the unknown norm of relative
translations between cameras based on the knowledge of relative rotations and
translation directions. We provide theoretical conditions for the solvability
of such a problem, and we propose a two-stage method to solve it. First, a
cycle basis for the epipolar graph is computed, then all the scaling factors
are recovered simultaneously by solving a homogeneous linear system. We
demonstrate the accuracy of our solution by means of synthetic and real
experiments.Comment: Accepted at 3DV 201
Spectral Motion Synchronization in SE(3)
This paper addresses the problem of motion synchronization (or averaging) and
describes a simple, closed-form solution based on a spectral decomposition,
which does not consider rotation and translation separately but works straight
in SE(3), the manifold of rigid motions. Besides its theoretical interest,
being the first closed form solution in SE(3), experimental results show that
it compares favourably with the state of the art both in terms of precision and
speed
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