2,378 research outputs found
The Affective Impact of Financial Skewness on Neural Activity and Choice
Few finance theories consider the influence of “skewness” (or large and asymmetric but unlikely outcomes) on financial choice. We investigated the impact of skewed gambles on subjects' neural activity, self-reported affective responses, and subsequent preferences using functional magnetic resonance imaging (FMRI). Neurally, skewed gambles elicited more anterior insula activation than symmetric gambles equated for expected value and variance, and positively skewed gambles also specifically elicited more nucleus accumbens (NAcc) activation than negatively skewed gambles. Affectively, positively skewed gambles elicited more positive arousal and negatively skewed gambles elicited more negative arousal than symmetric gambles equated for expected value and variance. Subjects also preferred positively skewed gambles more, but negatively skewed gambles less than symmetric gambles of equal expected value. Individual differences in both NAcc activity and positive arousal predicted preferences for positively skewed gambles. These findings support an anticipatory affect account in which statistical properties of gambles—including skewness—can influence neural activity, affective responses, and ultimately, choice
XMM-Newton observations of HD189733 during planetary transits
We report on two XMM-Newton observations of the planetary host star HD189733.
The system has a close in planet and it can potentially affect the coronal
structure via interactions with the magnetosphere. We have obtained X-ray
spectra and light curves from EPIC and RGS on board XMM-Newton which we have
analyzed and interpreted. We reduced X-ray data from primary transit and
secondary eclipse occurred in April 17th 2007 and May 18th 2009, respectively.
In the April 2007 observation only variability due to weak flares is
recognized. In 2009 HD189733 exhibited a X-ray flux always larger than in the
2007 observation. The average flux in 2009 was higher than in 2007 observation
by a factor of 45%. During the 2009 secondary eclipse we observed a softening
of the X-ray spectrum significant at level of ~3 sigma. Further, we observed
the most intense flare recorded at either epochs. This flare occurred 3 ks
after the end of the eclipse.The flare decay shows several minor ignitions
perhaps linked to the main event and hinting for secondary loops that emit
triggered by the main loop. Magneto-Hydro-Dynamical (MHD) simulations show that
the magnetic interaction between planet and star enhances the density and the
magnetic field in a region comprised between the planet and the star because of
their relative orbital/rotation motion. X-ray observations and model
predictions are globally found in agreement, despite the quite simple MHD model
and the lack of precise estimate of parameters including the alignment and the
intensity of stellar and planetary magnetic fields. Future observations should
confirm or disprove this hypothesis, by determining whether flares are
systematically recurring in the light curve at the same planetary phase.Comment: Accepted for publication on The Astrophysical Journa
Conditioning bounds for traveltime tomography in layered media
This paper revisits the problem of recovering a smooth, isotropic, layered
wave speed profile from surface traveltime information. While it is classic
knowledge that the diving (refracted) rays classically determine the wave speed
in a weakly well-posed fashion via the Abel transform, we show in this paper
that traveltimes of reflected rays do not contain enough information to recover
the medium in a well-posed manner, regardless of the discretization. The
counterpart of the Abel transform in the case of reflected rays is a Fredholm
kernel of the first kind which is shown to have singular values that decay at
least root-exponentially. Kinematically equivalent media are characterized in
terms of a sequence of matching moments. This severe conditioning issue comes
on top of the well-known rearrangement ambiguity due to low velocity zones.
Numerical experiments in an ideal scenario show that a waveform-based model
inversion code fits data accurately while converging to the wrong wave speed
profile
The Off Shell - Mixing in the QCD Sum Rules
The dependence of the mixing amplitude is analyzed with
the use of the QCD sum rules and the dispersion relation. Going off shell the
mixing decreases, changes sign at and is
negative in the space like region. Implications of this result to the isospin
breaking part of the nuclear force are discussed.Comment: 26 pages + 11 figures (PostScript
From uncertainty to reward: BOLD characteristics differentiate signaling pathways
<p>Abstract</p> <p>Background</p> <p>Reward value and uncertainty are represented by dopamine neurons in monkeys by distinct phasic and tonic firing rates. Knowledge about the underlying differential dopaminergic pathways is crucial for a better understanding of dopamine-related processes. Using functional magnetic resonance blood-oxygen level dependent (BOLD) imaging we analyzed brain activation in 15 healthy, male subjects performing a gambling task, upon expectation of potential monetary rewards at different reward values and levels of uncertainty.</p> <p>Results</p> <p>Consistent with previous studies, ventral striatal activation was related to both reward magnitudes and values. Activation in medial and lateral orbitofrontal brain areas was best predicted by reward uncertainty. Moreover, late BOLD responses relative to trial onset were due to expectation of different reward values and likely to represent phasic dopaminergic signaling. Early BOLD responses were due to different levels of reward uncertainty and likely to represent tonic dopaminergic signals.</p> <p>Conclusions</p> <p>We conclude that differential dopaminergic signaling as revealed in animal studies is not only represented locally by involvement of distinct brain regions but also by distinct BOLD signal characteristics.</p
Refined parameters of the planet orbiting HD 189733
We report on the BVRI multi-band follow-up photometry of the transiting
extrasolar planet HD 189733b. We revise the transit parameters and find
planetary radius RP = 1.154+/- 0.032RJ and inclination i_P = 85.79+/-0.24deg.
The new density (~ 1g cm-3) is significantly higher than the former estimate (~
0.75g cm-3); this shows that from the current sample of 9 transiting planets,
only HD 209458 (and possibly OGLE-10b) have anomalously large radii and low
densities. We note that due to the proximity of the parent star, HD 189733b
currently has one of the most precise radius determinations among extrasolar
planets. We calculate new ephemerides: P = 2.218573+/-0.000020 days, T0 =
2453629.39420+/-0.00024 (HJD), and estimate the timing offsets of the 11
distinct transits with respect to the predictions of a constant orbital period,
which can be used to reveal the presence of additional planets in the system.Comment: 10 pages, 4 figures, submitted to Ap
A Hopf laboratory for symmetric functions
An analysis of symmetric function theory is given from the perspective of the
underlying Hopf and bi-algebraic structures. These are presented explicitly in
terms of standard symmetric function operations. Particular attention is
focussed on Laplace pairing, Sweedler cohomology for 1- and 2-cochains, and
twisted products (Rota cliffordizations) induced by branching operators in the
symmetric function context. The latter are shown to include the algebras of
symmetric functions of orthogonal and symplectic type. A commentary on related
issues in the combinatorial approach to quantum field theory is given.Comment: 29 pages, LaTeX, uses amsmat
Planet-star interactions with precise transit timing: II. The radial-velocity tides and a tighter constraint on the orbital decay rate in the WASP-18 system
From its discovery, the WASP-18 system with its massive transiting planet on a tight orbit was identified as a unique laboratory for studies on tidal planet-star interactions. In an analysis of Doppler data, which include five new measurements obtained with the HIRES/Keck-I instrument between 2012 and 2018, we show that the radial velocity signal of the photosphere following the planetary tidal potential can be distilled for the host star. Its amplitude is in agreement with both theoretical predictions of the equilibriumtide approximation and an ellipsoidalmodulation observed in an orbital phase curve. Assuming a circular orbit, we refine system parameters using photometric time series from TESS. With a new ground-based photometric observation, we extend the span of transit timing observations to 28 yr in order to probe the rate of the orbital period shortening. Since we found no departure from a constant-period model, we conclude that the modified tidal quality parameter of the host star must be greater than 3.9×106with 95% confidence. This result is in line with conclusions drawn from studies of the population of hot Jupiters, predicting that the efficiency of tidal dissipation is 1 or 2 orders of magnitude weaker. As the WASP-18 system is one of the prime candidates for detection of orbital decay, further timing observations are expected to push the boundaries of our knowledge on stellar interiors.Fil: Maciejewski, G.. Nicolaus Copernicus University; PoloniaFil: Knutson, H. A.. California Institute of Technology; Estados UnidosFil: Howard, A. W.. University of Hawaii; Estados UnidosFil: Isaacson, H.. University of California at Berkeley; Estados UnidosFil: Fernandez Lajus, Eduardo Eusebio. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Instituto de Astrofísica La Plata. Universidad Nacional de La Plata. Facultad de Ciencias Astronómicas y Geofísicas. Instituto de Astrofísica La Plata; ArgentinaFil: Di Sisto, Romina Paula. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Instituto de Astrofísica La Plata. Universidad Nacional de La Plata. Facultad de Ciencias Astronómicas y Geofísicas. Instituto de Astrofísica La Plata; ArgentinaFil: Migaszewski, C.. Nicolaus Copernicus University; Poloni
Weak splittings of quotients of Drinfeld and Heisenberg doubles
We investigate the fine structure of the simplectic foliations of Poisson
homogeneous spaces. Two general results are proved for weak splittings of
surjective Poisson submersions from Heisenberg and Drinfeld doubles. The
implications of these results are that the torus orbits of symplectic leaves of
the quotients can be explicitly realized as Poisson-Dirac submanifolds of the
torus orbits of the doubles. The results have a wide range of applications to
many families of real and complex Poisson structures on flag varieties. Their
torus orbits of leaves recover important families of varieties such as the open
Richardson varieties.Comment: 20 pages, AMS Late
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