Black Ring Research Articles

Measuring the shape of a black hole photon ring

General relativity predicts that gravitational lensing near black holes will produce narrow "photon rings" on images. Building on recent work of Johnson, Lupsasca et al. focusing on circular rings, I calculate the long-baseline interferometric signature of a narrow feature of arbitrary shape and intensity. The shape information is contained in the oscillation frequencies of the complex visibility as a function of baseline length, for each baseline angle. These results raise the possibility of measuring the detailed shape of a photon ring and comparing to the precise predictions of general relativity.

Chaotic particle motion around a homogeneous circular ring

We consider test particle motion in a gravitational field generated by a homogeneous circular ring placed in $n$-dimensional Euclidean space. We observe that there exist no stable stationary orbits in $n=6, 7, \ldots, 10$ but exist in $n=3, 4, 5$ and clarify the regions in which they appear. In $n=3$, we show that the separation of variables of the Hamilton-Jacobi equation does not occur though we find no signs of chaos for stable bound orbits. Since the system is integrable in $n=4$, no chaos appears. In $n=5$, we find some chaotic stable bound orbits. Therefore, this system is nonintegrable at least in $n=5$ and suggests that the timelike geodesic system in the corresponding black ring spacetimes is nonintegrable.

Transfer and retention of oculomotor alignment rehabilitation training.

Ocular alignment defects such as strabismus affect around 5% of people and are associated with binocular vision impairments. Current nonsurgical treatments are controversial and have high levels of recidivism. In this study, we developed a rehabilitation method for ocular alignment training and examined the rate of learning, transfer to untrained alignments, and retention over time. Ocular alignment was controlled with a real-time dichoptic feedback paradigm where a static fixation target and white gaze-contingent ring were presented to the dominant eye and a black gaze-contingent ring with no fixation target was presented to the nondominant eye. Observers were required to move their eyes to center the rings on the target, with real-time feedback provided by the size of the rings. Offsetting the ring of the nondominant temporal or nasal visual field required convergent or divergent ocular deviation, respectively, to center the ring on the fixation target. Learning was quantified as the time taken to achieve target deviation of 2° (easy, E) or 4° (hard, H) for convergence (CE, CH) or divergence (DE, DH) over 40 trials. Thirty-two normally sighted observers completed two training sequences separated by one week. Subjects were randomly assigned to a training sequence: CE-CH-DE, CH-CE-DE, DE-DH-CE, or DH-DE-CE. The results showed that training was retained over the course of approximately one week across all conditions. Training on an easy deviation angle transferred to untrained hard angles within convergence or divergence but not between these directions. We conclude that oculomotor alignment can be rapidly trained, retained, and transferred with a feedback-based dichoptic paradigm. Feedback-based oculomotor training may therefore provide a noninvasive method for the rehabilitation of ocular alignment defects.

Diagnosis of viral diseases and revealing of candidates in nuclear plants of strawberry ex situ

Currently, about 20 viral diseases are known on strawberry in the world that can reduce the yield and its quality. According to the results of previous studies in the Moscow region, the prevalence of viruses on strawberries was: Arabis mosaic virus (ArMV) – 14 %, Raspberry ringspot virus (RpRSV) and Strawberry latent ringspot virus (SLRSV) – 16 %, Tomato black ring virus (TBRV) – 25 %. Viruses mainly spread in agrocenosis with infected planting material, with tools, with pollen and seeds, nematodes - longidorids (Xiphinema diversicaudatum – ArMV and SLRSV vector, Longidorus elongatus – RpRSV and TBRV vector). According to published data, the harmfulness of viruses on plants of strawberries was to reduce the number of repens by 6-40 %, outlets by 10-40 %, and ovaries by 30 %. The aim of the study was to study the species composition of viruses on strawberries to identify candidates for the nuclear plants. In serological tests, a sandwich ELISA was used according to the method “Diagnosis of pome and stone crops viruses by ELISA and PCR” (2008), for analysis, diagnostic kits from ‘Loewe’ (Germany) were used. Leaves were taken as samples. The analysis results were recorded on a ‘Stat Fax 2100’ tablet photometer at a wavelength of 405 and 630 nm. The species composition of viruses was studied on strawberry varieties and hybrids under ex situ conditions. The total prevalence of viruses was 29 %. 188 candidates for nuclear stock plants of 17 varieties and 2 hybrids of strawberry were revealed. No viruses were detected on varieties Barynya, Induka and promising hybrids 34-34-5 and 3-372-1, which may be associated with a low percentage of transmission of nepoviruses with seeds. After confirming the virus-free status of strawberry plants by PCR, they will receive the category of “nuclear stock plant”.

Prevalence of viral diseases and isolation of candidates in nuclear stock plants of raspberry ex situ

On raspberries, currently about 30 viral diseases are known in the world that can reduce the yield and its quality. According to the results of previous studies in the Moscow region, the prevalence of viruses on raspberries was: Arabis mosaic virus(ArMV) – 14 %, Raspberry ringspot virus(RpRSV) – 30 %, Strawberry latent ringspot virus(SLRSV) – 16 %, Tomato black ring virus (TBRV ) – 18 %, Raspberry bushy dwarf virus (RBDV) – 39 %. Viruses spread in agrocenosis with infected planting material, with tools, with pollen and seeds, nematodes – longidorids (Xiphinema diversicaudatum – ArMV and SLRSVvector, Longidorus elongatus – RpRSV and TBRVvector). The harmfulness of viruses on raspberry plants consisted inreducingthe productivity by 21 %, fruit masse– by 26 % compared with virus-free plants. The aim of the study was to study the species composition of viruses on raspberries to identify candidates for the nuclear stock plants. In serological tests, the ELISA sandwich version was used according, for analysis, diagnostic kits from Loewe (Germany) were used. Leaves were taken as samples. The results of analyzes were recorded on a Stat Fax 2100 hotometer at a wavelength of 405 and 630 nm. RBDV virus RNA was isolated using the CytoSorb kit, followed by RT-PCR. The species composition of viruses on raspberry varieties was studied under ex situ conditions. The total prevalence of viruses was 29 % with the predominance of the RBDV virus (19 %). 102 candidates for nuclearstockplants of 22 varieties of raspberries were identified. After confirming the virus-free status of raspberry plants by PCR, they will receive the category “nuclearstock plant”.

High-Resolution Temperature Variability Reconstructed from Black Pine Tree Ring Densities in Southern Spain

The presence of an ancient, high-elevation pine forest in the Natural Park of Sierras de Cazorla in southern Spain, including some trees reaching >700 years, stimulated efforts to develop high-resolution temperature reconstructions in an otherwise drought-dominated region. Here, we present a reconstruction of spring and fall temperature variability derived from black pine tree ring maximum densities reaching back to 1350 Coefficient of Efficiency (CE). The reconstruction is accompanied by large uncertainties resulting from low interseries correlations among the single trees and a limited number of reliable instrumental stations in the study region. The reconstructed temperature history reveals warm conditions during the early 16th and 19th centuries that were of similar magnitude to the warm temperatures recorded since the late 20th century. A sharp transition from cold conditions in the late 18th century (t1781–1810 = −1.15 °C ± 0.64 °C) to warm conditions in the early 19th century (t1818–1847 = −0.06 °C ± 0.49 °C) is centered around the 1815 Tambora eruption (t1816 = −2.1 °C ± 0.55 °C). The new reconstruction from southern Spain correlates significantly with high-resolution temperature histories from the Pyrenees located ~600 km north of the Cazorla Natural Park, an association that is temporally stable over the past 650 years (r1350–2005 > 0.3, p < 0.0001) and particularly strong in the high-frequency domain (rHF > 0.4). Yet, only a few of the reconstructed cold extremes (1453, 1601, 1816) coincide with large volcanic eruptions, suggesting that the severe cooling events in southern Spain are controlled by internal dynamics rather than external (volcanic) forcing.

Stability Analysis of Charged Rotating Black Ring

We study the electromagnetic field equation along with the WKB approximation. The boson tunneling phenomenon from charged rotating black ring (CRBR) is analyzed. It is examined that reserve radiation consistent with CRBR can be computed in general by neglecting back reaction and self-gravitational of the radiated boson particle. The calculated temperature depends upon quantum gravity and CRBR geometry. We also examine the corrected tunneling rate/probability of boson particles by assuming charge as well as energy conservation laws and the quantum gravity. Furthermore, we study the graphical behavior of the temperature and check the stability and instability of CRBR.

Stationary Black Holes and Light Rings.

The ringdown and shadow of the astrophysically significant Kerr black hole (BH) are both intimately connected to a special set of bound null orbits known as light rings (LRs). Does it hold that a generic equilibrium BH must possess such orbits? In this Letter we prove the following theorem. A stationary, axisymmetric, asymptotically flat black hole spacetime in 1+3 dimensions, with a nonextremal, topologically spherical, Killing horizon admits, at least, one standard LR outside the horizon for each rotation sense. The proof relies on a topological argument and assumes C^{2} smoothness and circularity, but makes no use of the field equations. The argument is also adapted to recover a previous theorem establishing that a horizonless ultracompact object must admit an even number of nondegenerate LRs, one of which is stable.

Genetic variability of Polish tomato black ring virus isolates and their satellite RNAs

AbstractTomato black ring virus (TBRV), a member of the Nepovirus genus, is a serious plant pathogen distributed worldwide. It causes significant damage to several economically important crops, such as artichoke or strawberry. The TBRV bipartite genome consists of two polyadenylated single‐stranded positive‐sense RNA molecules, which may be accompanied by subviral particles such as defective interfering RNAs (DI RNAs) and satellite RNAs (satRNAs). In this study, we obtained the complete genome sequence of six TBRV isolates originating from different hosts and determined the presence of eight TBRV satRNAs. Subsequently, genetic variability, recombination, phylogenetic and selection pressure analyses were performed. The results revealed that the TBRV population is genetically diverse. The occurrence of potential recombination events, evidence of positive selection pressure acting on particular codons and the diversification of satRNAs within the TBRV population indicated that the virus mutates and can rapidly adapt to new environmental conditions or hosts. The presented data shed some light on TBRV evolutionary dynamics and epidemiology.

Distorted black ring

We investigate how a static and neutral distribution of external matter distorts a 5-dimensional static black ring. We obtain a general expression for the distorted metric in terms of the background metric functions and the distortion fields, and find a multipole expansion for the latter. We demonstrate that the gravitational field of these external sources can be adjusted to remove the conical singularity of the undistorted black ring solution. We analyze properties of the distorted black ring for the specific cases of dipole and quadrupole distortions.

Black ripples, flowers and dumbbells at large D

We explore the rich phase space of singly spinning (both neutral and charged) black hole solutions in the large D limit. We find several ‘bumpy’ branches which are connected to multiple (concentric) black rings, and black Saturns. Additionally, we obtain stationary solutions without axisymmetry that are only stationary at D → ∞, but correspond to long-lived black hole solutions at finite D. These multipolar solutions can appear as intermediate configurations in the decay of ultra-spinning Myers-Perry black holes into stable black holes. Finally, we also construct stationary solutions corresponding to the instability of such a multipolar solution.

More on the entropy product and dual CFTs

In this paper, we check the universality of the entropy product for some black hole and black ring solutions. Applying the asymptotic symmetry group (ASG) analysis, we also find the central charges of the dual CFTs for these solutions. It has been observed [16] that if the entropy product for a solution is universal, it is possible to read the central charges of the dual CFTs from the entropy product as {c}_isim frac{partial }{partial {N}_i}left({S}_{+}{S}_{-}right), where Ni is a conserved charge of the solution like angular momentum or electric charge. In this work we consider some other families of solutions and we check that the same behavior is valid for them. Moreover, in the case of solutions containing the conical singularity, we find the central charges using the ASG analysis. We show that the central charges receive a contribution from the conical characteristic κ of the solution, however it is still possible to read the central charges from the entropy product.

Record of a 10-year old European Wildcat Felis silvestris silvestris Schreber, 1777 (Mammalia: Carnivora: Felidae) from Mt. Etna, Sicily, Italy

Longevity data for wild felids are lacking in the literature. Here we report a camera trap recapture of a European Wildcat Felis silvestris at Mt. Etna in Sicily, Italy after nine years. This individual was clearly identifiable as its tail ended with a white ring rather than the typical black ring and had a unique shape of the dorsal stripe. At first capture on 26 May 2009, this cat was assessed as an adult, so that the likely minimum age of this individual at the time of recapture on 10 June 2018 must have been be at least 10 years. This finding represents the oldest known European Wildcat in the wild and provides insight into age structure in wildcat populations.

Kerr-Schild double copy and complex worldlines

We use the classical double copy to identify a necessary condition for Maxwell theory sources to constitute single copies of Kerr-Schild solutions to Einstein’s equations. In the case of four-dimensional Kerr-Schild spacetimes on Minkowski backgrounds, we extend this condition to a parameterization of the corresponding single copies. These are given by Líenard-Wiechert fields of charges on complex worldlines. This unifies the known instances of the Kerr-Schild double copy black holes on flat four-dimensional backgrounds into a single framework. Furthermore, we use the more generic condition identified to show why the black ring in five dimensions does not admit Kerr-Schild coordinates.

Shadow of a Schwarzschild black hole surrounded by a Bach\u2013Weyl ring

We have studied the shadows of a Schwarzschild black hole surrounded by a Bach–Weyl ring through the backward ray-tracing method. The presence of Bach–Weyl ring leads to that the photon dynamical system is non-integrable and then chaos would appear in the photon motion, which affects sharply the black hole shadow. The size and shape the black hole shadow depend on the black hole parameter, the Bach–Weyl ring mass and the Weyl radius between black hole and ring. Some self-similar fractal structures also appear in the black hole shadow, which originates from the chaotic lensing. We also study the change of the image of Bach–Weyl ring with the ring mass and the Weyl radius. Finally, we analyze the invariant manifolds of Lyapunov orbits near the fixed points and discuss further the formation of the shadow of a Schwarzschild black hole with Bach–Weyl ring.

Electron Microscopy of In-Plaque Phage T3 Assembly: Proposed Analogs of Neurodegenerative Disease Triggers.

Increased knowledge of virus assembly-generated particles is needed for understanding both virus assembly and host responses to virus infection. Here, we use a phage T3 model and perform electron microscopy (EM) of thin sections (EM-TS) of gel-supported T3 plaques formed at 30 °C. After uranyl acetate/lead staining, we observe intracellular black particles, some with a difficult-to-see capsid. Some black particles (called LBPs) are larger than phage particles. The LBP frequency is increased by including proflavine, a DNA packaging inhibitor, in the growth medium and increasing plaque-forming temperature to 37 °C. Acidic phosphotungstate-precipitate (A-PTA) staining causes LBP substitution by black rings (BRs) that have the size and shape expected of hyper-expanded capsid containers for LBP DNA. BRs are less frequent in liquid cultures, suggesting that hyper-expanded capsids evolved primarily for in-gel (e.g., in-biofilm) propagation. BR-specific A-PTA staining and other observations are explained by α-sheet intense structure of the major subunit of hyper-expanded capsids. We hypothesize that herpes virus triggering of neurodegenerative disease occurs via in-gel propagation-promoted (1) generation of α-sheet intense viral capsids and, in response, (2) host production of α-sheet intense, capsid-interactive, innate immunity amyloid protein that becomes toxic. We propose developing viruses that are therapeutic via detoxifying interaction with this innate immunity protein.

Visual-Inertial Fusion Based Positioning Systems

In this paper, we developed a visible light positioning (VLP) system using a camera and low-cost inertial measurement units (IMUs). Applying computer vision and sensor fusion techniques, our VLP system is able to estimate the angle of arrival (AoA) and the distance from a landmark to a mobile device. Due to the complementary nature between IMUs and cameras, we are able to improve the performance of VLP systems by applying sensor fusion. Currently, most optical positioning systems require at least two line-of-sight (LOS) links, so the coverage is not always satisfactory. Using a single round light-emitting diode (LED) panel or two coplanar black thick rings as the landmark, our VLP system only needs one LOS link to estimate the orientation and position of the mobile device. By activating inertial navigation, our VLP system is able to perform localization even if the landmark is temporarily blocked by obstacles. We derived approximated upper bounds of the angular errors and applied visual-inertial sensor fusion in estimating the Euler angles of the mobile device. Since the weights of sensor fusion are determined by upper bounds, the expected maximum errors are minimized in our positioning system. In our field experiments, the positioning system has an average positioning error of 0.18m with an effective positioning range of 7m. Compared to similar types of positioning systems, our system has significant improvements in positioning range without sacrificing positioning accuracy.

Soil conditions required for reaction wood formation of drunken trees in a continuous permafrost region

ABSTRACT Black spruce trees lean to form “drunken” forest on degrading permafrost; however, the causes of tree leaning on continuous permafrost remain unclear. Leaning events are recorded by reaction wood formation in tree rings, and it remains unclear what soil conditions are required for reaction wood formation of drunken trees. Tree disk morphology and soil hummock properties were examined for fifty tree–mound combinations in Northwest Territories, Canada. Spruce trees growing on mound edges form reaction wood on the downslope sides of their trunks. Reaction wood formation in mature trees was greatest in stem tissues between ground level and 30 cm aboveground. Reaction wood formation occurred only in trees growing on mound edges. The extent of reaction wood formation was higher in trees growing in clayey soils than in trees on sandy soils. For trees growing on clayey mound edges, the extent of reaction wood formation decreased with increasing permafrost table depth. Black spruce tree rings formed between ground level and 30 cm aboveground could record movement of clayey soil hummocks over shallow, underlying permafrost tables. A combination of clayey soil texture and shallow permafrost table is likely required for development of hummocks and drunken forests on the continuous permafrost region studied.

Ортштейни дерново-підзолистих поверхнево-оглеєних ґрунтів Прибескидського Передкарпаття

On the basis of morphological and laboratory-analytical researches it is established that in the profile of sod-podzolic pseudogleyed soils of the Beskydy Precarpathians are formed ortsteins that have clear outer contours, concentric inner structure with alternation of rust-red circles. Two ranges for the formation of ortsteins in the investigation soils were established: in the overiluvial part of the profile and the transition to the rock horizon. Within the НЕgl horizon, the content of ortsteins is 2.8 %, and in the fractional composition, the fraction is from 2.1 to 3.0 mm (37.5 %). The highest content of ortsteins (7.7 %) is characteristic of the Ehgl horizon, within which the fraction from 7.1 to 10.0 mm (27.2 %) prevails. Within the Pigl horizon, large ortsteins of 1.0 to 5.0 cm in size are oval and tubular with a concentric inner structure, and their content is 17.6 %. Ortsteins in the sod-podzolic pseudogleyed soils were formed as a result of alternation of redox conditions with the participation of specific, nonspecific microflora and glesish-eluvial, segregation processes of soil formation. The small ortsteins in the overiluvial part of the profile are the result of modern soil formation, and the large ones within the Pigl horizon are relict and associated with the early stages of soil formation in the Precarpathians. In order to identify the genesis and elemental composition, a plate of tubular ortstein with a diameter of 1.2 cm, which was selected from the Pigl horizon (220–240 cm), was made. In different parts of the plate, differing in colour, four points up to 1 μm in size (two against a light background and two against a dark one) were selected, within which elemental composition was determined by micro-X-ray spectrometry. The measurements were performed on a scanning electron microscope REM-106 (Ukraine) with a resolution of 5 nm and an energy-dispersive X-ray detector. The study of ortstein using a scanning electron microscope revealed that the formation of black rings within the tubular ortstein is due to an increase in the percentage of Manganese in 1.6–3.4, Aluminium in 1.4–2.3 and Calcium in 2.1–5.4 times. The percentage of Ferum in different parts of the ortstein is approximately the same, which determines its rusty-brown colour. Key words: ortsteins, sod-podzolic pseudogleyed soils, Beskydy Precarpathians, the accumulation factor, electron-scanning microscope.

Universality of the area product: Solutions with conical singularity

It has been observed that the area product of horizons for many black hole solutions is mass independent and satisfy the universality relation $A_+A_-=(8\pi)^2 N$, where $N$ is related to the quantized charges of the solution as angular momentum and electric charge. In this work the same analysis is done for black hole and black ring solutions with conical singularity. We find that the area product is still mass independent and regardless of the horizon topology, the conical characteristic ($\kappa$) of the solutions, appears in the universality relation as $\kappa A_+A_-=(8\pi)^2 N$. We also check that the first law of black hole inner mechanics is satisfied for these solutions.