1,362,183 research outputs found
The class of the affine line is a zero divisor in the Grothendieck ring
No full textWe show that the class of the affine line is a zero divisor in the Grothendieck ring of algebraic varieties over complex numbers. The argument is based on the Pfaffian-Grassmannian double mirror correspondence.Peer reviewe
A JOURNEY FROM THE OCTONIONIC P2 TO A FAKE P2
No full textWe discover a family of surfaces of general type with K2 = 3 and pg = q = 0 as free C13 quotients of special linear cuts of the octonionic projective plane OP2. A special member of the family has 3 singularities of type A2, and is a quotient of a fake projective plane. We use the techniques of earlier work of Borisov and Fatighenti to define this fake projective plane by explicit equations in its bicanonical embedding
A journey from the octonionic P2 to a fake P2
No full textWe discover a family of surfaces of general type with K2=3
and pg=q=0 as free C13 quotients of special linear cuts of the octonionic projective plane OP2. A special member of the family has
3 singularities of type A2, and is a quotient of a fake projective plane. We use the techniques of earlier work of Borisov and Fatighenti to define this fake projective plane by explicit equations in its bicanonical embedding
Professor Aleksandr Evgenevich Borisov (on the 70th anniversary of the birth).
No full textAlexander Evgenievich Borisov – head of the Department of surgery named after N. D. Monastyrskii (Available at: https://www.livelib.ru/author/733938/series-aleksandr-borisov
Cometary observations in light-polluted environments: a case study of interstellar comet 2I/Borisov
No full textComets and asteroids have long captured human curiosity, and until recently, all documented examples belonged to our Solar System. That changed with the discovery of the first known interstellar object, 1I/2017 U1 (‘Oumuamua), in 2017. Two years later, on August 30, 2019, Gennady Borisov discovered a second interstellar object, 2019 Q4, which was officially designated 2I/Borisov. From its initial images, the object’s diffuse appearance hinted at its cometary nature. To better understand the photometric evolution of comet 2I/Borisov as it traveled through the inner Solar System, we compiled observations using medium-sized telescopes. This data is crucial for gaining insights into its size and composition, as well as how such objects, after millions of years in interstellar space, behave when exposed to the Sun’s radiation. Given that 2I/Borisov is the first interstellar comet ever observed, constraining its behavior is of great scientific interest. In this paper, we present photometric data gathered from observatories in Crimea and Catalonia, highlighting the importance of systematic photometric studies of interstellar objects using meter-class telescopes. Our observations showed a steady increase in the comet’s brightness as it approached perihelion, likely due to the slow sublimation of ices. Over the five-month pre-perihelion observation period, we did not detect any significant changes in magnitude. The analysis of observations reveals a steady increase in comet 2I/Borisov brightness as it approached perihelion, likely due to the sublimation of ices, with no observable outbursts during the five-month pre-perihelion period. Additionally, we discuss the challenges in ground-based observation of comets posed by light pollution today, particularly in urban areas, where visual observations are severely limited. Using sample surface brightness measurements, we demonstrate the impact of light pollution and outline the importance of systematic photometric studies for interstellar objects.We acknowledge support from the Spanish Ministry of Science and Innovation, research projects PGC2018-097374-B-I00 and PID2021-128062NB-I00 (PI: JMTR), funded by FEDER/Ministerio de Ciencia e Innovación – Agencia Estatal de Investigación, the Academy of Finland project no. 325806 “PlanetS” (PI: MG), and the Centre for Innovation and Transfer of Natural Sciences and Engineering Knowledge, University of Rzeszów, Poland (RPPK.01.03.00-18-001/10-00). The programme of development within Priority-2030 is acknowledged for supporting the research at UrFU. We thank Herbert Raab for his kind support with Astrometrica software. We also thank the feedback received from A. Fraser Gillan. TJO images at OAdM were scheduled by Toni Santana (UB).Open Access funding provided thanks to the CRUE-CSIC agreement with Springer Nature.Peer reviewe
Unusual polarimetric properties for interstellar comet 2I/Borisov
No full textSo far, only two interstellar objects have been observed within our Solar System. While the first one, 1I/‘Oumuamua, had asteroidal characteristics, the second one, 2I/Borisov, showed clear evidence of cometary activity. We performed polarimetric observations of comet 2I/Borisov using the European Southern Observatory Very Large Telescope to derive the physical characteristics of its coma dust particles. Here we show that the polarization of 2I/Borisov is higher than what is typically measured for Solar System comets. This feature distinguishes 2I/Borisov from dynamically evolved objects such as Jupiter-family and all short- and long-period comets in our Solar System. The only object with similar polarimetric properties as 2I/Borisov is comet C/1995 O1 (Hale-Bopp), an object that is believed to have approached the Sun only once before its apparition in 1997. Unlike Hale-Bopp and many other comets, though, comet 2I/Borisov shows a polarimetrically homogeneous coma, suggesting that it is an even more pristine object.This work is based on observations made with ESO Telescopes at the La Silla Paranal Observatory thanks to Director Discretionary Time under programme ID 2104.C-5003. The work of T.S.-R. was carried out through grant APOSTD/2019/046 by Generalitat Valenciana (Spain). This work was supported by the MINECO (Spanish Ministry of Economy) through grant RTI2018-095076-B-C21 (MINECO/FEDER, UE)
Kurven und Flächen im dreidimensionalen Raum mit Absolutem, das aus zwei reellen Ebenen und zwei reellen Punkten ihrer gemeinsamen Geraden besteht
No full text[Borisov Adrian; Borisov A.; Borisov Adrijan V.; Borisov Adriyan V.; Borisov Andriyan; Борисов Адриян]Bulgarian. Russian, German summar
О конгруэнциях прямых в трехмерном пространстве с абсолютом двумя реальными точками и одной реальной плоскостью, проходящей через одну из них
No full text[Borisov Adrian; Borisov A.; Borisov Adrijan V.; Borisov Adriyan V.; Borisov Andriyan; Борисов Адриян]Bulgarian. Russian, English summar
A colour portrait of the interstellar comet 2I/Borisov
No full textThe aim of this paper is to report on the results of a multicolour observing campaign performed at the LBT on the interstellar comet 2I/Borisov during three epochs while target was approaching its perihelion: UBVRI images have been observed in October and December 2019, when the comet was at ∼2.3 and 2.0 au from the Sun, respectively. Comet Borisov presented a rather complex morphology, especially in the December observing epoch, when a bi-lobate structure on a global scale was visible, with a jet-like structure characterised by a disconnection event, probably due to the presence of an active area on the nucleus' surface combined with its rotational properties. U – B colour, measured for the first time for this comet, monotonically decreases as Borisov approaches perihelion, from 0.35 ± 0.05 in October 19th to −0.07 ± 0.05 in December 2nd; B – V colour shows a more chaotic behaviour, with values for October epochs quite similar to solar colours, and a higher value of 0.76 ± 0.04 in December 2nd, probably due to a combination of an increase of the B flux (CN emission) and of an increase in V flux (due to C2). V – R and R–I colours derived in both the October and December observing epochs depict a scenario of a coma slightly redder than the Sun, with a RI-reddening value of ∼11%/1000 Å and ∼5%/1000 Å, respectively. The R- Afρ at the reference aperture of r ∼104 km from the optocentre slightly decreases from ∼100 cm (October) to ∼ 70 cm (December), showing that the Borisov's dust environment is quite similar to those of Short Period Comets of our Solar System. The application of a first-order photometric model, with the plausible scenario of grains with radius a = 100 μm and bulk density ρd = 1000 kg/m3 moving at vd in the range of 3–30 m/s, allows to derive a dust production rate Qd decrease from a range of 3–25 kg/s in October to a range of 2–18 kg/s in December. All these results confirm that the interstellar comet 2I/Borisov has a coma environment quite similar to that of the Short Period Comets (mostly Jupiter Family targets) orbiting in our inner Solar System
Geradenkongruenzen im dreidimensionalen Raum, dessen absolutes Gebilde aus zwei reellen Ebenen und zwei reellen Punkten auf deren Schnittlinie besteht
No full text[Borisov Adrian V.; Borisov A.; Borisov Adrijan V.; Borisov Adriyan V.; Borisov Andriyan; Борисов Адриян В.]Bulgarian. Russian, German summar
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