60,374 research outputs found
Small deviations of iterated processes in space of trajectories
We derive logarithmic asymptotics of probabilities of small deviations for
iterated processes in the space of trajectories. We find conditions under which
these asymptotics coincide with those of processes generating iterated
processes. When these conditions fail the asymptotics are quite different
Four hot DOGs eaten up with the EVN
Hot dust-obscured galaxies (hot DOGs) are a rare class of hyperluminous
infrared galaxies recently identified with the Wide-field Infrared Survey
Explorer (WISE) satellite. The majority of the ~1000-member all-sky population
should be at high redshifts (z~2-3), at the peak of star formation in the
history of the Universe. This class most likely represents a short phase during
galaxy merging and evolution, a transition from starburst- to AGN-dominated
phases. For the first time, we observed four hot DOGs with known mJy-level
radio emission using the European VLBI Network (EVN) at 1.7 GHz, in a hope to
find compact radio features characteristic to AGN activity. All four target
sources are detected at ~15-30 mas angular resolution, confirming the presence
of an active nucleus. The sources are spatially resolved, i.e. the flux density
of the VLBI-detected components is smaller than the total flux density,
suggesting that a fraction of the radio emission originates from larger-scale
(partly starburst-related) activity. Here we show the preliminary results of
our e-EVN observations made in 2014 February, and discuss WISE J1814+3412, an
object with kpc-scale symmetric radio structure, in more detail.Comment: 6 pages, 1 figure; appears in the proceedings of the 12th European
VLBI Network Symposium and Users Meeting (7-10 October 2014, Cagliari,
Italy), eds. A. Tarchi, M. Giroletti & L. Feretti. JREF Proceedings of
Science, PoS(EVN 2014)003,
http://pos.sissa.it/archive/conferences/230/003/EVN%202014_003.pd
Two in one? A possible dual radio-emitting nucleus in the quasar SDSS J1425+3231
The radio-emitting quasar SDSS J1425+3231 (z=0.478) was recently found to
have double-peaked narrow [O III] optical emission lines. Based on the analysis
of the optical spectrum, Peng et al. (2011) suggested that this object harbours
a dual active galactic nucleus (AGN) system, with two supermassive black holes
(SMBHs) separated on the kpc scale. SMBH pairs should be ubiquitous according
to hierarchical galaxy formation scenarios in which the host galaxies and their
central black holes grow together via interactions and eventual mergers. Yet
the number of presently-confirmed dual SMBHs on kpc or smaller scales remains
small. A possible way to obtain direct observational evidence for duality is to
conduct high-resolution radio interferometric measurements, provided that both
AGN are in an evolutionary phase when some activity is going on in the radio.
We used the technique of Very Long Baseline Interferometry (VLBI) to image SDSS
J1425+3231. Observations made with the European VLBI Network (EVN) at 1.7 GHz
and 5 GHz frequencies in 2011 revealed compact radio emission at sub-mJy flux
density levels from two components with a projected linear separation of
\sim2.6 kpc. These two components support the possibility of a dual AGN system.
The weaker component remained undetected at 5 GHz, due to its steep radio
spectrum. Further study will be necessary to securely rule out a jet--shock
interpretation of the less dominant compact radio source. Assuming the dual AGN
interpretation, we discuss black hole masses, luminosities, and accretion rates
of the two components, using available X-ray, optical, and radio data. While
high-resolution radio interferometric imaging is not an efficient technique to
search blindly for dual AGN, it is an invaluable tool to confirm the existence
of selected candidates.Comment: 7 pages, 2 figures. Accepted for publication in Monthly Notices of
the Royal Astronomical Societ
On the choice of colliding beams to study deformation effects in relativistic heavy ion collisions
It has been suggested that collisions between deformed shapes will lead to
interesting effects on various observables such as K production and elliptic
flow. Simple formulae can be written down which show how to choose the
colliding beams which will maximise the effects of deformation.Comment: 2 pages, this version supersedes the previous on
Large deviations for solutions to stochastic recurrence equations under Kesten's condition
In this paper we prove large deviations results for partial sums constructed
from the solution to a stochastic recurrence equation. We assume Kesten's
condition [Acta Math. 131 (1973) 207-248] under which the solution of the
stochastic recurrence equation has a marginal distribution with power law
tails, while the noise sequence of the equations can have light tails. The
results of the paper are analogs to those obtained by A. V. Nagaev [Theory
Probab. Appl. 14 (1969) 51-64; 193-208] and S. V. Nagaev [Ann. Probab. 7 (1979)
745-789] in the case of partial sums of i.i.d. random variables. In the latter
case, the large deviation probabilities of the partial sums are essentially
determined by the largest step size of the partial sum. For the solution to a
stochastic recurrence equation, the magnitude of the large deviation
probabilities is again given by the tail of the maximum summand, but the exact
asymptotic tail behavior is also influenced by clusters of extreme values, due
to dependencies in the sequence. We apply the large deviation results to study
the asymptotic behavior of the ruin probabilities in the model.Comment: Published in at http://dx.doi.org/10.1214/12-AOP782 the Annals of
Probability (http://www.imstat.org/aop/) by the Institute of Mathematical
Statistics (http://www.imstat.org
"Knowledge-Capital, International Trade and Foreign Direct Investment: A Sectoral Analysis"
The knowledge-capital (KC) model of MNEs is now a widely adopted empirical approach to explaining the location and production decisions of global firms based on both horizontal and vertical motivations. While most of the existing studies have focused on highly aggregated national data, we extend this model to sectoral data consisting of broad manufacturing industries and explicitly account for the dynamic nature of international investment data. The empirical results from a dynamic panel data analysis indicate that that the predictions of the KC model regarding MNE behavior vary by the type of industry. Production processes in electronics and transportation-equipment are more characterized by efficient vertical specialization of R&D activities and assembly, while other sectors display more complex motivations.FDI, knowledge-capital model, exports, GMM
Vibrational Modes in LiBC: Theory Compared with Experiment
The search for other superconductors in the MgB2 class currently is focussed
on Li{1-x}BC, which when hole-doped (concentration x) should be a metal with
the potential to be a better superconductor than MgB2. Here we present the
calculated phonon spectrum of the parent semiconductor LiBC. The calculated
Raman-active modes are in excellent agreement with a recent observation, and
comparison of calculated IR-active modes with a recent report provides a
prediction of the LO--TO splitting for these four modes, which is small for the
B-C bond stretching mode at ~1200 cm^{-1}, but large for clearly resolved modes
at 540 cm^{-1} and 620 cm^{-1}.Comment: 4 pages, two embedded figures. Physica B (in press
- …