Masses and Mixing of cqqˉqˉc q \bar{q} \bar{q} Tetraquarks Using Glozman-Riska Hyperfine Interaction

In this paper we perform a detailed study of the masses and mixing of the single charmed scalar tetraquarks: $c q \bar{q} \bar{q}$. We also give a systematic analysis of these tetraquark states by weight diagrams, quantum numbers and flavor wave functions. Tetraquark masses are calculated using four different fits. The following SU(3)$_\mathrm{F}$ representations are discussed: $\bar{15}_\mathrm{S}$, $\bar{3}_\mathrm{S}$, $6_\mathrm{A}$ and $\bar{3}_\mathrm{A}$. We use the flavor-spin Glozman-Riska interaction Hamiltonian with SU(3) flavor symmetry breaking. There are 27 different tetraquarks composed of a charm quark $c$ and of the three light flavors $u, d, s$: 11 cryptoexotic (3 D$_\mathrm{s}^{+}$, 4 D$^{+}$, 4 D$^{0}$) and 16 explicit exotic states. We discuss D$_\mathrm{s}$ and its isospin partners in the same multiplet, as well as all the other four-quark states. Some explicit exotic states appear in the spectrum with the same masses as D$_\mathrm{s}^{+}$(2632) in $\bar{15}_\mathrm{S}$ and with the same masses as D$_\mathrm{s}^{+}$(2317) in $6_\mathrm{A}$ representation, which confirm the tetraquark nature of these states.Comment: 10 pages, 6 tables, 6 figures. Accepted for publication in Phys. Rev.

Constraints on RnR^n gravity from precession of orbits of S2-like stars: a case of a bulk distribution of mass

Here we investigate possible applications of observed stellar orbits around Galactic Center for constraining the R$^n$ gravity at Galactic scales. For that purpose, we simulated orbits of S2-like stars around the massive black hole at Galactic Center, and study the constraints on the R$^n$ gravity which could be obtained by the present and next generations of large telescopes. Our results show that R$^n$ gravity affects the simulated orbits in the qualitatively similar way as a bulk distribution of matter (including a stellar cluster and dark matter distributions) in Newton's gravity. In the cases where the density of extended mass is higher, the maximum allowed value of parameter $\beta$ in R$^n$ gravity is noticeably smaller, due to the fact that the both extended mass and $R^n$ gravity cause the retrograde orbital precession.Comment: 10 pages, 4 figures, accepted for publication in Advances in Space Researc

Constraining Scalar-Tensor gravity models by S2 star orbits around the Galactic Center

The aim of our investigation is to derive a particular theory among the class of scalar-tensor(ST) theories of gravity, and then to test it by studying kinematics and dynamics of S-stars around supermassive black hole (BH) at Galactic Center (GC). We also discuss the Newtonian limit of this class of ST theories of gravity, as well as its parameters. We compare the observed orbit of S2 star with our simulated orbit which we obtained theoretically with the derived ST potential and constrained the parameters. Using the obtained best fit parameters we calculated orbital precession of S2 star in ST gravity,and found that it has the same direction as in General Relativity (GR), but causes much larger pericenter shift.Comment: 13 pages, 1 table, 6 figures. Accepted for publication in Facta Universitatis: Series Phys. Chem. Tech. (Invited lecture at Balkan Workshop 2018

Distribution of radio spectral index over the Lupus loop

We use all-sky surveys at 408 and 1420 MHz with aim to investigate properties of the Galactic radio source Lupus Loop. We estimate the brightness temperature, surface brightness and radio spectral index of this supernova remnant using the method we have developed. The non-thermal nature of its radiation is confirmed, and also the distribution of spectral index over its area is given

Study of spectral index of giant radio galaxy from Leahy's Atlas: DA 240

Here we investigate the giant radio galaxy DA 240, which is a FR II source. Specifically, we investigate its flux density, as well as the spectral index distribution. For that purpose, we used publicly available data for the source: Leahy's atlas of double radio-sources and NASA/IPAC Extragalactic Database (NED). We used observations at 326 MHz (92 cm) and at 608 MHz (49 cm) and obtained spectral index distributions between 326 and 608 MHz. For the first time we give spectral index map for these frequencies. We found that the synchrotron radiation is the dominant radiation mechanism over most of the area of DA 240, and also investigated the mechanism of radiation at some characteristic points, namely its core and the hotspots. The results of this study will be helpful for understanding the evolutionary process of the DA 240 radio source

Estimation of P{X < Y} for gamma exponential model

In this paper, we estimate probability P{X < Y} when X and Y are two independent random variables from gamma and exponential distribution, respectively. We obtain maximum likelihood estimator and its asymptotic distribution. We perform some simulation study

Flux densities and spectral indices of Relaxed Double radio galaxy 3C 84

Here we study the flux densities distribution at 1380, 4908 and 15365 MHz, as well as the radio spectral index of 3C 84, a Double Radio source Associated with Galactic Nucleus (DRAGN). 3C 84 is the dominant giant elliptical galaxy in the Perseus cluster, and thus very interesting for our research. This famous radio galaxy Perseus A has Relaxed Double classification because it has the large halo, with the lack of its compact structure. We show its structure (using 2D and 3D flux density plot). Besides, we calculated the radio spectral index, which we then used to investigate the nature and mechanisms of its radiation. The obtained values of spectral indices indicated that the northern hotspot is dominated by synchrotron radiation, while in southern hotspot there are thermal and non-thermal radiations, depending on the studied frequency pairs.BPU11 : 11th International Conference of the Balkan Physical Union : Proceedings book; Aug 11 - Sep 1, 2022S02-AA Astronomy and Astrophysic

Katarakta, operacija oka, afakija i hromatska ekspresija slikara Jovana Bijelića

Background/Aim. Approaching art from the standpoint of optics and the artist's eye pathology can sometimes explain the shift of the spectral colors in the work of some artists with cataract and aphakia. This may not be obvious in the paintings of other artists with the same eye pathology. The aim of this study was to create a timeline from the recently obtained details of the cataract surgery, his best corrected aphakic visual acuity, and the last paintings of the artist Jovan Bijelić. Methods. The research included primary and secondary source material: Bijelić's paintings from all stages of his career, interviews with Bijelić and his eye surgeon, art criticism, sources with the description of Bijelić's symptoms, hospital archives, discussion with art historians, comparison of his palette from different periods. Results. Jovan Bijelić was nearly blind from cataract in 1957. He underwent an unsuccessful cataract surgery in 1956, followed by enucleation of the operated eye. In 1958, 20/25-20/20 vision was regained, after the extracapsular cataract extraction and sector iridectomy in his right eye, with the posterior lens capsule discision afterwards. Xanthopsia and cyanopsia are not present in his art, which is not a representation of visualized objects. Conclusion. The response of Jovan Bijelić to cataract and aphakia was predominantly a change of his style.Uvod/Cilj. Pristup umetnosti sa stanovišta optike i patologije umetnikovog oka može ponekad da objasni skretanje spektralnih boja u radovima nekih slikara sa kataraktom i afakijom. Kod drugih umetnika sa istom patologijom ove promene ne moraju biti očigledne. Cilj ovog rada bio je da se istraži odgovor slikara Jovana Bijelića na kataraktu i afakiju upoređivanjem novih podataka o njegovoj katarakti, operaciji i najbolje korigovanoj afaknoj oštrini vida sa slikama nastalim u tom periodu. Metode. Podaci su prikupljeni pretraživanjem primarnih i sekundarnih izvora: Bijelićevih slika iz svih perioda njegovog rada, novinskih članaka i intervjua sa Bijelićem i njegovim hirurgom, umetničkim kritikama, izvorima sa opisima Bijelićevih simptoma, arhivima klinika, razgovorima sa istoričarem umetnosti i slikarem. Rezultati. Jovan Bijelić je bio gotovo slep 1957. Jedno oko mu je bilo neuspešno operisano od katarakte 1956, a kasnije i enukleisano. Posle ekstrakapsularne ekstrakcije sa iridektomijom i kasnijom discizijom kapsule, desnom oku je dve godine kasnije vraćena odlična oštrina vida od 0.9-1.0. Ksantopsija i cijanopsija nisu prisutne u Bijlićevom slikarstvu jer on nije prikazivao posmatrane, već imaginarne predmete, često menjajući stil. Zaključak. Odgovor slikara Jovana Bijelića na kataraktu i afakiju prevashodno se manifestovao u promeni stila

Sindrom Urets-Zavalia nastao posle duboke prednje lamelarne keratoplastike

Introduction. Urrets-Zavalia syndrome is an uncommon complication of the deep anterior lamellar keratoplasty in keratoconus. The manifestations of this syndrome are an irreversible mydriasis, iris atrophy and secondary glaucoma. Case report. Deep anterior lamellar keratoplasty was done for keratoconus with a presumably healed corneal hydrops in a 21-year-old Caucasian man. The graft remained clear, but the surgery was complicated by a fixed, dilated pupil, patches of iris atrophy, ectropium of the iris pigment layer and glaukomflecken in the lens. Conclusion. Although safer than penetrating keratoplasty, the deep anterior lamellar corneal transplantation is not devoid of complications. Urrets-Zavalia syndrome can be avoided by not trying to secure an unhealed Descemet's membrane with air. Instead, a new Descemet's membrane transplanted within a penetrating graft is a safer choice.Uvod. Sindrom Urets-Zavalije je neuobičajena komplikacija posle operacije keratokonusa metodom duboke prednje lamelarne keratoplastike. Manifestacije ovog sindroma su trajna midrijaza, atrofija dužice i sekundarni glaukom. Prikaz bolesnika. Kod bolesnika starog 21 godinu, urađena je duboka prednja lamelarna keratoplastika sa keratokonusom i naizgled zaceljenim hidropsom rožnjače. Kalem je ostao providan, ali se operacija komplikovala trajnom midrijazom, poljima atrofije dužice, izvrnutim rubom pigmentnog sloja dužice i mrljastim zamućenjima ispod prednje kapsule sočiva (glaukomflecken). Zaključak. Mada bezbednija od perforativne keratoplastike, duboka prednja lamelarna transplantacija rožnjače nije bez komplikacija. Sindrom Urets-Zavalije može se izbeći ako se umesto zaptivanja otvora u Descemetovoj membrani pomoću vazduha, presadi nova Descemetova membrana zajedno sa kalemom, tehnikom perforativne keratoplastike