233 research outputs found
Dissipation in the hagedorn early universe
The viscosity coefficients of the Hagedorn hadronic matter are obtained by solving the Boltzmann kinetic equation in the relaxation-time approximation. The upper limit for the increase of entropy per baryonic charge was found to be < 10 in the "hadron era" of the Friedman universe and the model behaves almost like dust-filled models. There is no anisotropy damping in the Bianchi type I universe but a substantial growth of entropy is possible in that era when anisotropy has an extremely high value
Cosmic-Ray Acceleration at Ultrarelativistic Shock Waves: Effects of Downstream Short-Wave Turbulence
The present paper is the last of a series studying the first-order Fermi
acceleration processes at relativistic shock waves with the method of Monte
Carlo simulations applied to shocks propagating in realistically modeled
turbulent magnetic fields. The model of the background magnetic field structure
of Niemiec & Ostrowski (2004, 2006) has been augmented here by a
large-amplitude short-wave downstream component, imitating that generated by
plasma instabilities at the shock front. Following Niemiec & Ostrowski (2006),
we have considered ultrarelativistic shocks with the mean magnetic field
oriented both oblique and parallel to the shock normal. For both cases
simulations have been performed for different choices of magnetic field
perturbations, represented by various wave power spectra within a wide
wavevector range. The results show that the introduction of the short-wave
component downstream of the shock is not sufficient to produce power-law
particle spectra with the "universal" spectral index 4.2. On the contrary,
concave spectra with cutoffs are preferentially formed, the curvature and
cutoff energy being dependent on the properties of turbulence. Our results
suggest that the electromagnetic emission observed from astrophysical sites
with relativistic jets, e.g. AGN and GRBs, is likely generated by particles
accelerated in processes other than the widely invoked first-order Fermi
mechanism.Comment: 9 pages, 8 figures, submitted to Ap
Study of GRB light curve decay indices in the afterglow phase
In this work we study the distribution of temporal power-law decay indices,
, in the Gamma Ray Burst (GRB) afterglow phase, fitted for GRBs
(139 long GRBs, 12 short GRBs {\it with extended emission} and 25 X-Ray Flashes
(XRFs)) with known redshifts. These indices are compared with the temporal
decay index, , derived with the light curve fitting using the
\cite{willingale07} model. This model fitting yields similar distributions of
to the fitted , but for individual bursts a difference can
be significant. Analysis of (, ) distribution, where is the
characteristic luminosity at the end of the plateau, reveals only a weak
correlation of these quantities. However, we discovered a significant regular
trend when studying GRB values along the \cite{dainotti2008}
correlation between and the end time of the plateau emission in the rest
frame, , hereafter LT correlation. We note a systematic variation of the
parameter distribution with luminosity for any selected . We
analyze this systematics with respect to the fitted LT correlation line,
expecting that the presented trend may allow to constrain the GRB physical
models. We also attempted to use the derived correlation of
versus to diminish the luminosity scatter related to the variations
of along the LT distribution, a step forward in the effort of
standardizing GRBs. A proposed toy model accounting for this systematics
applied to the analyzed GRB distribution results in a slight increase of the LT
correlation coefficient.Comment: Accepted for publication in Ap
Longterm Optical Monitoring of Bright BL Lacertae Objects with ATOM: Spectral Variability and Multiwavelength Correlations
Blazars are the established sources of an intense and variable non-thermal
radiation extending from radio wavelengths up to HE and VHE gamma-rays.
Understanding the spectral evolution of blazars in selected frequency ranges,
as well as multi-frequency correlations in various types of blazar sources, is
of a primary importance for constraining the blazar physics. Here we present
the results of a long-term optical monitoring of a sample of 30 blazars of the
BL Lac type. We study the optical color-magnitude correlation patterns emerging
in the analyzed sample, and compare the optical properties of the targets with
the high-energy gamma-ray and high-frequency radio data. The optical
observations were carried out in R and B filters using ATOM telescope. Each
object was observed during at least 20 nights in the period 2007-2012. We find
significant global color-magnitude correlations in 40 % of the sample. The
sources which do not display any clear chromatism often do exhibit
bluer-when-brighter (bwb) behavior but only in isolated shorter time intervals.
We also discovered spectral state transitions at optical wavelengths in several
sources. Finally, we find that the radio, optical, and gamma-ray luminosities
of the sources obey almost linear correlations, which seem however induced, at
least partly, by the redshift dependance, and may be also affected by
non-simultaneousness of the analyzed dataset. We argue that the observed bwb
behavior is intrinsic to the jet emission regions, at least for some of the
analyzed blazars, rather than resulting from the contamination of the measured
flux by the starlight of host galaxies. We also conclude that the significance
of color-magnitude scalings does not correlate with the optical color, but
instead seems to depend on the source luminosity, in a sense that these are the
lowest-luminosity BL Lac objects which display the strongest correlations.Comment: 16 pages, 9 figures, accepted for publication in Astronomy &
Astrophysic
Cosmic-ray Acceleration at Ultrarelativistic Shock Waves: Effects of a "Realistic" Magnetic Field Structure
First-order Fermi acceleration processes at ultrarelativistic shocks are
studied with Monte Carlo simulations. The accelerated particle spectra are
derived by integrating the exact particle trajectories in a turbulent magnetic
field near the shock. ''Realistic'' features of the field structure are
included. We show that the main acceleration process at superluminal shocks is
the particle compression at the shock. Formation of energetic spectral tails is
possible in a limited energy range only for highly perturbed magnetic fields,
with cutoffs occuring at low energies within the resonance energy range
considered. These spectral features result from the anisotropic character of
particle transport in the downstream magnetic field, where field compression
produces effectively 2D perturbations. Because of the downstream field
compression, the acceleration process is inefficient in parallel shocks for
larger turbulence amplitudes, and features observed in oblique shocks are
recovered. For small-amplitude turbulence, wide-energy range particle spectra
are formed and modifications of the process due to the existence of long-wave
perturbations are observed. In both sub- and superluminal shocks, an increase
of \gamma leads to steeper spectra with lower cut-off energies. The spectra
obtained for the ``realistic'' background conditions assumed here do not
converge to the ``universal'' spectral index claimed in the literature. Thus
the role of the first-order Fermi process in astrophysical sources hosting
relativistic shocks requires serious reanalysis.Comment: submitted to Ap
Comparison of the results of modified NDVI indicator established on the basis of measurements by hyperspectral spectrometer and digital camera
Due to the lack of readily available imaging remote sensing methods that would determine the vegetation state on a local scale, an attempt was made to calculate the modified NDVI index on the basis of digital camera photography. To verify the effectiveness of the method, the digital camera and hyperspectral spectrometer results were compared. For the analysis material leaves of six different tree species from an urban area were selected and picked in four different phases of the vegetative season. The results prove that there is no significant correlation between the two methods, but they also suggest that further research on the proposed method is necessary.
Problem wydatków sztywnych w budżecie państwa oraz zmieniającym się środowisku polskich finansów publicznych
This article deals with a problem of budget rigidities. At the outset, the doctrinal definitions of budged rigidities were cited and analyzed. On this basis, the Author developed a catalogue of rigidities, the elements of which were later classified into appropriate expenditure groups. In the further part of the work, methods of making ridged expenses more flexible are presented. Then, the problem of an excessive increase in budged rigidities is presented in the context of the marginalization of the state budget process that has been progressing in recent years. On the basis of the current processes taking place in the fiscal policy, the author indicates the need to consider the described problem in a wider context.W artykule wskazano problem państwowych wydatków sztywnych. Na wstępie przytoczone i przeanalizowane zostały doktrynalne definicje wydatków sztywnych. Na tej podstawie opracowano katalog wydatków sztywnych, którego elementy później zostały zaklasyfikowane do odpowiednich grup wydatkowych. W dalszej części pracy przytoczone są metody „uelastyczniania wydatków sztywnych” w zależności od ich źródła. Następnie problem nadmiernego wzrostu wydatków sztywnych zestawiony zostaje z postępującą w ostatnich latach marginalizacją budżetu państwa. Na podstawie obecnych procesów zachodzących w polityce fiskalnej wskazano na konieczność rozpatrywania opisywanego problemu w szerszym obszarze niż budżet państwa
Modyfikacje konstrukcji stabilizującej reguły wydatkowej w 2021 roku
This article is focused on an analysis of amendments introduced to Articles 112aa and 112d of the Public Finance Act which were adopted by Act of 11 August 2021 amending the Public Finance Act and certain other acts. At the beginning, a structure of the stabilising expenditure rule mechanism is briefly described. In this part of the text first-made changes are also outlined. Then, reasons for introducing subsequent amendments and form of each of these changes are thoroughly analysed. On this basis, conclusions are drawn as to the impact of the modification on the functioning of the stabilizing expenditure rule in the following years.Przedmiotem artykułu jest analiza zmian w art. 112aa i art. 112d ustawy o finansach publicznych, które zostały uchwalone na mocy ustawy z dnia 11 sierpnia 2021 r. o zmianie ustawy o finansach publicznych oraz niektórych innych ustaw. Na wstępie krótkiemu opisowi została poddana konstrukcja mechanizmu SRW oraz nakreślone zostały jego wcześniejsze zmiany. Następnie dogłębnej analizie poddane zostały przyczyny i forma każdej z omawianych zmian. Na tej podstawie zostały wyciągnięte wnioski co do wpływu modyfikacji na funkcjonowanie stabilizującej reguły wydatkowej w następnych latach
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