814 research outputs found
Nonthermal Emission Associated with Strong AGN Outbursts at the Centers of Galaxy Clusters
Recently, strong AGN outbursts at the centers of galaxy clusters have been
found. Using a simple model, we study particle acceleration around a shock
excited by an outburst and estimate nonthermal emission from the accelerated
particles. We show that emission from secondary electrons is consistent with
the radio observations of the minihalo in the Perseus cluster, if there was a
strong AGN outburst >~10^8 yrs ago with an energy of ~1.8x10^62 erg. The
validity of our model depends on the frequency of the large outbursts. We also
estimate gamma-ray emission from the accelerated particles and show that it
could be detected with GLAST.Comment: Accepted for publication in ApJ
Radiation Spectra from Advection-Dominated Accretion Flows in a Global Magnetic Field
We calculate the radiation spectra from advection-dominated accretion flows
(ADAFs), taking into account the effects of a global magnetic field.
Calculation is based on the analytic model for magnetized ADAFs proposed by
Kaburaki, where a large-scale magnetic field controls the accretion process.
Adjusting a few parameters, we find that our model can well reproduce the
observed spectrum of Sagittarius A. The result is discussed in comparison
with those of well-known ADAF models, where the turbulent viscosity controls
the accretion process.Comment: Accepted for publication in Ap
Types of Technological Entrepreneurs: a Study in a Large Emerging Economy
This study identifies the profiles of technological entrepreneurs. Understanding what drives entrepreneurs can help policy design to incentivize entrepreneurship, support the development of better assistance for nascent businesses, and facilitate the matching between investors’ and entrepreneurs’ interests. Through the application of an online questionnaire, 325 Brazilian owners of technological startups answered their reasons to enterprise. The data was processed using Ward’s hierarchical clustering algorithm, generating four distinct clusters. The first, financial success entrepreneurs, are concerned about financial outcomes of their startups. The new challenges group seeks self-realization, innovation, and independence by means of their enterprises. Leaders are driven by the will to lead and motivate others, relegating other factors. Finally, there are pessimistic entrepreneurs, who rank all reasons lower than other entrepreneurs. These results highlight that even within the class of technological entrepreneurs, from the same country, there are sizeable groups with different factors regarding reasons to enterprise, shedding some light on conflicting results in the entrepreneurial motivation literature
Energetics of Tev Blazars and Physical Constraints on their Emission Regions
Using multi-frequency spectra from TeV blazars in quiescent states, we obtain
the physical parameters of the emission region of blazars within the framework
of the one-zone synchrotron self-Compton (SSC) model. We numerically calculate
the steady-state energy spectra of electrons by self-consistently taking into
account the effects of radiative cooling with a proper account of the
Klein-Nishina effects. Here electrons are assumed to be injected with a
power-law spectrum and to escape on a finite time scale, which naturally leads
to the existence of a break energy scale. Although we do not use time
variabilities but utilize a model of electron escape to constrain the size of
the emission region, the resultant size turns out to be similar to that
obtained based on time variabilities. Through detailed comparison of the
predicted emission spectra with observations, we find that for Mrk 421, Mrk
501, and PKS 2155--304, the energy density of relativistic electrons is about
an order of magnitude larger than that of magnetic fields with an uncertainty
within a factor of a few.Comment: Accepted for publication in Ap
Equation of state in the PNJL model with the entanglement interaction
The equation of state and the phase diagram in two-flavor QCD are
investigated by the Polyakov-loop extended Nambu--Jona-Lasinio (PNJL) model
with an entanglement vertex between the chiral condensate and the
Polyakov-loop. The entanglement-PNJL (EPNJL) model reproduces LQCD data at zero
and finite chemical potential better than the PNJL model. Hadronic degrees of
freedom are taken into account by the free-hadron-gas (FHG) model with the
volume-exclusion effect due to the hadron generation. The EPNJL+FHG model
improves agreement of the EPNJL model with LQCD data particularly at small
temperature. The quarkyonic phase survives, even if the correlation between the
chiral condensate and the Polyakov loop is strong and hadron degrees of freedom
are taken into account. However, the location of the quarkyonic phase is
sensitive to the strength of the volume exclusion.Comment: 9 pages, 7 figure
Nuclear g-Factor of the 2972 keV Isomer in 130Xe
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