7,929 research outputs found
Investor Competence, Trading Frequency, and Home Bias
People are more willing to bet on their own judgments when they feel skillful or knowledgeable (Heath and Tversky (1991)). We investigate whether this "competence effect" influences trading frequency and home bias. We find that investors who feel competent trade more often and have a more internationally diversified portfolio. We also find that male investors, and investors with higher income or more education, are more likely to perceive themselves as competent investors than are female investors, and investors with lower income or less education. Our results are unlikely to be explained by other hypotheses, such as overconfidence or information advantage. Finally, we separately establish a link between optimism towards the home market and international portfolio diversification.
On the proof of some theorem on locally nilpotent subgroups in division rings
In Hai-Thin (2009), there is a theorem, stating that every locally nilpotent
subnormal subgroup in a division ring is central (see Hai-Thin (2009, Th.
2.2)). Unfortunately, there is some mistake in the proof of this theorem. In
this note we give the another proof of this theorem.Comment: 3 page
Diquark Higgs at LHC
Existence of color sextet diquark Higgs fields with TeV masses will indicate
a fundamentally different direction for unification than conventional grand
unified theories. There is a class of partial unification models based on the
gauge group that implement the seesaw
mechanism for neutrino mass with seesaw scale around GeV, where
indeed such light fields appear naturally despite the high gauge symmetry
breaking scale. They couple only to up-type quarks in this model.
We discuss phenomenological constraints on these fields and show that they
could be detected at LHC via their decay to either or single top + jet. We
also find that existing Tevatron data gives a lower bound on its mass somewhere
in the 400-500 GeV, for reasonable values of its coupling.Comment: 5 pages, 3 figure
Population synthesis of accreting white dwarfs: II. X-ray and UV emission
Accreting white dwarfs (WDs) with non-degenerate companions are expected to
emit in soft X-rays and the UV, if accreted H-rich material burns stably. They
are an important component of the unresolved emission of elliptical galaxies,
and their combined ionizing luminosity may significantly influence the optical
line emission from warm ISM. In an earlier paper we modeled populations of
accreting WDs, first generating WD with main-sequence, Hertzsprung gap and red
giant companions with the population synthesis code \textsc{BSE}, and then
following their evolution with a grid of evolutionary tracks computed with
\textsc{MESA}. Now we use these results to estimate the soft X-ray
(0.3-0.7keV), H- and He II-ionizing luminosities of nuclear burning WDs and the
number of super-soft X-ray sources for galaxies with different star formation
histories. For the starburst case, these quantities peak at Gyr and
decline by orders of magnitude by the age of 10 Gyr. For stellar
ages of ~10 Gyr, predictions of our model are consistent with soft X-ray
luminosities observed by Chandra in nearby elliptical galaxies and He II
4686 line ratio measured in stacked SDSS spectra of retired
galaxies, the latter characterising the strength and hardness of the UV
radiation field. However, the soft X-ray luminosity and
He~II~4686 ratio are significantly overpredicted for stellar
ages of Gyr. We discuss various possibilities to resolve this
discrepancy and tentatively conclude that it may be resolved by a modification
of the typically used criteria of dynamically unstable mass loss for giant
stars.Comment: 13 pages, 12 figures, MNRAS accepte
Next generation population synthesis of accreting white dwarfs: I. Hybrid calculations using BSE + MESA
Accreting, nuclear-burning white dwarfs have been deemed to be candidate
progenitors of type Ia supernovae, and to account for supersoft X-ray sources,
novae, etc. depending on their accretion rates. We have carried out a binary
population synthesis study of their populations using two algorithms. In the
first, we use the binary population synthesis code \textsf{BSE} as a baseline
for the "rapid" approach commonly used in such studies. In the second, we
employ a "hybrid" approach, in which we use \textsf{BSE} to generate a
population of white dwarfs (WD) with non-degenerate companions on the verge of
filling their Roche lobes. We then follow their mass transfer phase using the
detailed stellar evolution code \textsf{MESA}. We investigate the evolution of
the number of rapidly accreting white dwarfs (RAWDs) and stably nuclear-burning
white dwarfs (SNBWDs), and estimate the type Ia supernovae (SNe Ia) rate
produced by "single-degenerate" systems (SD). We find significant differences
between the two algorithms in the predicted numbers of SNBWDs at early times,
and also in the delay time distribution (DTD) of SD SNe Ia. Such differences in
the treatment of mass transfer may partially account for differences in the SNe
Ia rate and DTD found by different groups. Adopting 100\% efficiency for helium
burning, the rate of SNe Ia produced by the SD-channel in a Milky-way-like
galaxy in our calculations is , more than an
order of magnitude below the observationally inferred value. In agreement with
previous studies, our calculated SD DTD is inconsistent with observations.Comment: 13 pages,11 figures, accepted by MNRA
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