1,722 research outputs found
The valuation of N-phased investment projects under jump-diffusion processes
In this paper we consider N-phased investment opportunities where the time evolution of the project value follows a jump-diffusion process. An explicit valuation formula is derived under two different scenarios: in the first case we consider fixed and certain investment costs and in the second case we consider cost uncertainty and assume that investment costs follow a jump-diffusion process
The effects of environmental taxes and quotas on the optimal timing of emission reductions under Choquet-Brownian uncertainty
The effects of two environmental policy options for the reduction of pollution emissions, i.e. taxes and non-tradable quotas, are analyzed. In contrast to the prior literature this work endogenously takes into account the level of emissions before and after the adoption of the new environmental policy. The level of emissions is determined by solving the firm's profit maximization problem under taxes and fixed quotas. We find that the optimal adoption threshold under taxes is always larger than the adoption threshold under fixed quota, even in a setting characterized by ecological uncertainty and ambiguity - in the form of Choquet-Brownian motions - on future costs and benefits over adopting environmental policies.
A Model for Evaluating Pharmaceutical R&D Investment Projects under Technical and Economic Uncertainties
This study sets up a compound option approach for evaluating pharmaceutical R&D investment projects in the presence of technical and economic uncertainties. Technical uncertainty is modeled as a Poisson jump that allows for failure and thus abandonment of the drug development. Economic uncertainty is modeled as a standard di¤usion process which incorporates both up-and downward shocks. Practical application of this method is emphasized through a case analysis. We show that both uncertainties have a positive impact on the R&D option value. Moreover, from the sensitivity analysis, we nd that the sensitivity of the option with respect to economic uncertainty and market introduction cost decreases when technical uncertainty increases
From "universal" profiles to "universal" scaling laws in X-ray galaxy clusters
As the end products of the hierarchical process of cosmic structure
formation, galaxy clusters present some predictable properties, like those
mostly driven by gravity, and some others, more affected by astrophysical
dissipative processes, that can be recovered from observations and that show
remarkable "universal" behaviour once rescaled by halo mass and redshift.
However, a consistent picture that links these universal radial profiles and
the integrated values of the thermodynamical quantities of the intracluster
medium, also quantifying the deviations from the standard self-similar
gravity-driven scenario, has to be demonstrated. In this work, we use a
semi-analytic model based on a universal pressure profile in hydrostatic
equilibrium within a cold dark matter halo with a defined relation between mass
and concentration to reconstruct the scaling laws between the X-ray properties
of galaxy clusters. We also quantify any deviation from the self-similar
predictions in terms of temperature dependence of a few physical quantities
such as the gas mass fraction, the relation between spectroscopic temperature
and its global value, and, if present, the hydrostatic mass bias. This model
allows to reconstruct both the observed profiles and the scaling laws between
integrated quantities. We use the Planck-selected ESZ sample to calibrate the
predicted scaling laws between gas mass, temperature, luminosity and total
mass. Our universal model reproduces well the observed thermodynamic properties
and provides a way to interpret the observed deviations from the standard
self-similar behaviour. By combining these results with the constraints on the
observed relation, we show how we can quantify the level of gas
clumping affecting the studied sample, estimate the clumping-free gas mass
fraction, and suggest the average level of hydrostatic bias present.Comment: 13 pages. A&A in press. Minor update to fix typos and better match
published versio
An assessment of the measurement of the Lense-Thirring effect in the Earth gravity field, in reply to: ``On the measurement of the Lense-Thirring effect using the nodes of the LAGEOS satellites, in reply to ``On the reliability of the so far performed tests for measuring the Lense-Thirring effect with the LAGEOS satellites'' by L. Iorio,'' by I. Ciufolini and E. Pavlis
In this paper we reply to recent claims by Ciufolini and Pavlis about certain
aspects of the measurement of the general relativistic Lense-Thirring effect in
the gravitational field of the Earth. I) The proposal by such authors of using
the existing satellites endowed with some active mechanism of compensation of
the non-gravitational perturbations as an alternative strategy to improve the
currently ongoing Lense-Thirring tests is unfeasible because of the impact of
the uncancelled even zonal harmonics of the geopotential and of some
time-dependent tidal perturbations. II) It is shown that their criticisms about
the possibility of using the existing altimeter Jason-1 and laser-ranged Ajisai
satellites are groundless.III) Ciufolini and Pavlis also claimed that we would
have explicitly proposed to use the mean anomaly of the LAGEOS satellites in
order to improve the accuracy of the Lense-Thirrring tests. We prove that it is
false. In regard to the mean anomaly of the LAGEOS satellites, Ciufolini
himself did use such an orbital element in some previously published tests.
About the latest test performed with the LAGEOS satellites, IV) we discuss the
cross-coupling between the inclination errors and the first even zonal harmonic
as another possible source of systematic error affecting it with an additional
9% bias. V) Finally, we stress the weak points of the claims about the origin
of the two-nodes LAGEOS-LAGEOS II combination used in that test.Comment: LaTex2e, 22 pages, no figures, no tables. To appear in Planetary and
Space Science. Reference Ries et al. 2003a added and properly cite
A Free-Form Lensing Grid Solution for A1689 with New Mutiple Images
Hubble Space Telescope imaging of the galaxy cluster Abell 1689 has revealed
an exceptional number of strongly lensed multiply-imaged galaxies, including
high-redshift candidates. Previous studies have used this data to obtain the
most detailed dark matter reconstructions of any galaxy cluster to date,
resolving substructures ~25 kpc across. We examine Abell 1689 (hereafter,
A1689) non-parametrically, combining strongly lensed images and weak
distortions from wider field Subaru imaging, and we incorporate member galaxies
to improve the lens solution. Strongly lensed galaxies are often locally
affected by member galaxies, however, these perturbations cannot be recovered
in grid based reconstructions because the lensing information is too sparse to
resolve member galaxies. By adding luminosity-scaled member galaxy deflections
to our smooth grid we can derive meaningful solutions with sufficient accuracy
to permit the identification of our own strongly lensed images, so our model
becomes self consistent. We identify 11 new multiply lensed system candidates
and clarify previously ambiguous cases, in the deepest optical and NIR data to
date from Hubble and Subaru. Our improved spatial resolution brings up new
features not seen when the weak and strong lensing effects are used separately,
including clumps and filamentary dark matter around the main halo. Our
treatment means we can obtain an objective mass ratio between the cluster and
galaxy components, for examining the extent of tidal stripping of the luminous
member galaxies. We find a typical mass-to-light ratios of M/L_B = 21 inside
the r<1 arcminute region that drops to M/L_B = 17 inside the r<40 arcsecond
region. Our model independence means we can objectively evaluate the
competitiveness of stacking cluster lenses for defining the geometric
lensing-distance-redshift relation in a model independent way.Comment: 23 pages with 25 figures Replced with MNRAS submitted version. Some
figures have been corrected and minor text edit
On Gravitational Waves in Spacetimes with a Nonvanishing Cosmological Constant
We study the effect of a cosmological constant on the propagation
and detection of gravitational waves. To this purpose we investigate the
linearised Einstein's equations with terms up to linear order in in a
de Sitter and an anti-de Sitter background spacetime. In this framework the
cosmological term does not induce changes in the polarization states of the
waves, whereas the amplitude gets modified with terms depending on .
Moreover, if a source emits a periodic waveform, its periodicity as measured by
a distant observer gets modified. These effects are, however, extremely tiny
and thus well below the detectability by some twenty orders of magnitude within
present gravitational wave detectors such as LIGO or future planned ones such
as LISA.Comment: 8 pages, 4 figures, accepted for publication in Physical Review
First preliminary tests of the general relativistic gravitomagnetic field of the Sun and new constraints on a Yukawa-like fifth force from planetary data
The general relativistic Lense-Thirring precessions of the perihelia of the
inner planets of the Solar System are about 10^-3 arcseconds per century.
Recent improvements in planetary orbit determination may yield the first
observational evidence of such a tiny effect. Indeed, corrections to the known
perihelion rates of -0.0036 +/- 0.0050, -0.0002 +/- 0.0004 and 0.0001 +/-
0.0005 arcseconds per century were recently estimated by E.V. Pitjeva for
Mercury, the Earth and Mars, respectively, on the basis of the EPM2004
ephemerides and a set of more than 317,000 observations of various kinds. The
predicted relativistic Lense-Thirring precessions for these planets are
-0.0020, -0.0001 and -3 10^-5 arcseconds per century, respectively and are
compatible with the determined perihelia corrections. The relativistic
predictions fit better than the zero-effect hypothesis, especially if a
suitable linear combination of the perihelia of Mercury and the Earth, which a
priori cancels out any possible bias due to the solar quadrupole mass moment,
is considered. However, the experimental errors are still large. Also the
latest data for Mercury processed independently by Fienga et al. with the INPOP
ephemerides yield preliminary insights about the existence of the solar
Lense-Thirring effect. The data from the forthcoming planetary mission
BepiColombo will improve our knowledge of the orbital motion of this planet
and, consequently, the precision of the measurement of the Lense-Thirring
effect. As a by-product of the present analysis, it is also possible to
constrain the strength of a Yukawa-like fifth force to a 10^-12-10^-13 level at
scales of about one Astronomical Unit (10^11 m).Comment: LaTex, 22 pages, 1 figure, 5 tables, 62 references. To appear in
Planetary and Space Scienc
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