Search results for "lazar"
showing 10 items of 91 documents
The influence of the magnetic field on the spectral properties of blazars
2013
We explore the signature imprinted by dynamically relevant magnetic fields on the spectral energy distribution (SED) of blazars. It is assumed that the emission from these sources originates from the collision of cold plasma shells, whose magnetohydrodynamic evolution we compute by numerically solving Riemann problems. We compute the SEDs including the most relevant radiative processes and scan a broad parameter space that encompasses a significant fraction of the commonly accepted values of not directly measurable physical properties. We reproduce the standard double hump SED found in blazar observations for unmagnetized shells, but show that the prototype double hump structure of blazars …
Dynamical efficiency of collisionless magnetized shocks in relativistic jets
2010
The so-called internal shock model aims to explain the light-curves and spectra produced by non-thermal processes originated in the flow of blazars and gamma-ray bursts. A long standing question is whether the tenuous collisionless shocks, driven inside a relativistic flow, are efficient enough to explain the amount of energy observed as compared with the expected kinetic power of the outflow. In this work we study the dynamic efficiency of conversion of kinetic-to- thermal/magnetic energy of internal shocks in relativistic magnetized outflows. We find that the collision between shells with a non-zero relative velocity can yield either two oppositely moving shocks (in the frame where the co…
LOFAR measures the hotspot advance speed of the high-redshift blazar S5 0836+710
2019
Our goal is to study the termination of an AGN jet in the young universe and to deduce physical parameters of the jet and the intergalactic medium. We use LOFAR to image the long-wavelength radio emission of the high-redshift blazar S5 0836+710 on arcsecond scales between 120 MHz and 160 MHz. The LOFAR image shows a compact unresolved core and a resolved emission region about 1.5 arcsec to the southwest of the radio core. This structure is in general agreement with previous higher-frequency radio observations with MERLIN and the VLA. The southern component shows a moderately steep spectrum with a spectral index of about $\gtrsim -1$ while the spectral index of the core is flat to slightly i…
Limits on neutrino Lorentz violation from multimessenger observations of TXS 0506+056
2019
The observation by the IceCube Collaboration of a high-energy ($E \gtrsim 200$ TeV) neutrino from the direction of the blazar TXS 0506+056 and the coincident observations of enhanced $\gamma$-ray emissions from the same object by MAGIC and other experiments can be used to set stringent constraints on Lorentz violation in the propagation of neutrinos that is linear in the neutrino energy: $\Delta v = - E/M_1$, where $\Delta v$ is the deviation from the velocity of light, and $M_1$ is an unknown high energy scale to be constrained by experiment. Allowing for a difference in neutrino and photon propagation times of $\sim 10$ days, we find that $M_1 \gtrsim 3 \times 10^{16}$ GeV. This improves …
Coincidence of a high-fluence blazar outburst with a PeV-energy neutrino event
2016
The discovery of extraterrestrial very-high-energy neutrinos by the IceCube collaboration has launched a quest for the identification of their astrophysical sources. Gamma-ray blazars have been predicted to yield a cumulative neutrino signal exceeding the atmospheric background above energies of 100 TeV, assuming that both the neutrinos and the gamma-ray photons are produced by accelerated protons in relativistic jets. Since the background spectrum falls steeply with increasing energy, the individual events with the clearest signature of being of an extraterrestrial origin are those at PeV energies. Inside the large positional-uncertainty fields of the first two PeV neutrinos detected by Ic…
Fugitives in transit. The Spanish Republican exile through Portugal (1936-1950)
2017
Despite scant attention from historiography, Portugal played an important role as a way station on the road to exile for many Republicans during and after the Spanish Civil War. The situation in the neighbouring country was not easy for these people, as Antonio Oliveira de Salazar’s regime —officially allied with Franco’s Spain— did not recognize them as political refugees, but as illegal immigrants to be returned to Spain, which would have catastrophic consequences for many of them. Through the analysis of abundant primary sources in archives from Spain, Portugal, Mexico and the United States, we seek to understand the details of this Portuguese stage of the exile. We discover how, despite…
Some families of big and stable bundles on $K3$ surfaces and on their Hilbert schemes of points
2021
Here we investigate meaningful families of vector bundles on a very general polarized $K3$ surface $(X,H)$ and on the corresponding Hyper--Kaehler variety given by the Hilbert scheme of points $X^{[k]}:= {\rm Hilb}^k(X)$, for any integer $k \geqslant 2$. In particular, we prove results concerning bigness and stability of such bundles. First, we give conditions on integers $n$ such that the twist of the tangent bundle of $X$ by the line bundle $nH$ is big and stable on~$X$; we then prove a similar result for a natural twist of the tangent bundle of $X^{[k]}$. Next, we prove global generation, bigness and stability results for tautological bundles on $X^{[k]}$ arising either from line bundles…
Brief an Garlieb H. Merkel
1799
Ms. 930a, Nr. 8, Bl. 22r-23v Böttiger, Karl August. Brief an Garlieb H. Merkel, Weimar, d[en] 13. November 1797 Autora rokraksts / Autograph, vācu, angļu un latīņu val. / Deutsch, Englisch und Latein [4] lpp. / S. Attēlu numuri / Bildnummern: 930a-008-1 – 930a-008-4 Der Verfasser nennt in diesem inhaltsreichen Brief zahlreiche Namen und hält nicht nur die Verbindung mit Merkel, die aus dessen erstem Aufenthalt in Weimar resultierte, aufrecht, sondern gibt ihm weitere Hinweise und Empfehlung für seinen weiteren Aufenthalt in Dänemark. So rät er zur Übersetzung dreier Romane aus dem Englischen, darunter Jane Wests „A gossip's story“ (London 1796). Ferner bittet der Verfasser Merkel um Gefälli…
Der pikareske Roman als Katalysator in geschichtlichen Abläufen : erzählerische Kommunikationsmodelle in Das Leben des Lazarillo von Tormes, bei Thom…
2005
Anna-Riitta Tunturi tutki väitöskirjassaan pikareski- eli veijariromaanin eri ilmenemismuotoja historiallisena läpileikkauksena, sosiologisena ilmiönä ja romaanitaiteen osa-alueena. Sana ”pícaro” tulee kastiliankielen verbistä ”picar”, joka tarkoittaa alempiarvoisten ammattien harjoittamista, kuten picador de toros, pikadori härkätaistelussa, toreadorin avustaja. Saksaksi sana on Schelm, joten oma sanamme kelmi on saksalaista lainaa. Lisäksi suomen kielessä on veijari, huijari, heittiö tai hulttio, ja lisääkin varmasti löytyy. This dissertation in comparative literature examines several Finnish picaresque novels of 20th century in relation to some classical continental European novels such …