Holographic Aspects of Even-Dimensional Topological Gravity

In an odd-dimensional spacetime, gravity can be formulated as a proper gauge theory based on the Chern-Simons action for a suitable gauge group. Performing dimensional reduction, one obtains, as an effective theory, Chamseddine's even-dimensional topological gravity with the reduced gauge symmetry. This theory involves a multiplet of scalar fields that appear as a result of the dimensional reduction, and it is topological in the sense that its action does not depend on the metric. Focusing primarily on the four-dimensional case, we use the holographic dictionary to compute one-point correlation functions of the relevant boundary operators and find that the spin-current can have a nonzero expectation value in the dual quantum field theory. We also consider the generalized holographic Weyl anomaly and find that it vanishes. Finally, we propose a way of computing two-point correlation functions using the gravitational Wilson lines.Comment: 12 page

Aproksimacije rešenja stohastičkih diferencijalnih jednačina primenom Taylor-ovih redova

The subject of the doctoral dissertation is the application of the Taylor formula for the coefficients of various types of stochastic differential equations, for the purpose of the approximation of theirs solutions under non standard conditions, such as the global Lipschitz condition and the linear growth condition. Under certain assumptions, the almost sure convergence and the convergence in the p-th mean, p>0, of the sequence of approximate solutions towards the solution of the initial equation, is shown. The rate of the Lp convergence increases as the orders of the Taylor approximations of the coefficients of the initial equation increase. Shown results are illustrated through the examples which are designed such that the global Lipschitz condition and/or the linear growth condition for the drift and diffusion coefficients are not satisfied. That way, the need for the shown results is satisfied. Techniques used in the proofs are determined by the type of the considered equation, as well as by the conditions which are assumed for the coefficients of the equations

Nail metal connector plate - experimental determination of load-bearing capacity of timber member connections

This paper demonstrates the results of experimental determination of load-bearing capacity of structural timber member connections realized by nail metal connector plates which represent a new type of mechanical fasteners in load-bearing timber structures. The application of this type of metal connector should eliminate weakness of the standard metal connector plates produced by sheet perforating and pulling the teeth perpendicular to a sheet plane. The aim of the conducted experimental study was to determine the load-bearing capacity of connections realized by nail metal connector plates, in accordance with the provisions of Eurocode 5. Experimental testing was conducted by loading of multiple samples up to the limit bearing capacity of connection realized by nail metal connector plate. Discussion of the test results included the analysis of the limit bearing capacity of connection for different values of connection displacements, comparison of the obtained results with characteristic load-bearing capacity of standard type of metal connectors and with load-bearing capacity of nails calculated in accordance with limit state theory. Review of the determined limit bearing capacities of realized connections was given in the conclusion, together with the comment on test results, for the purpose of improving the application of metal connectors in modern systems of timber structures

Uporedna analiza funkcionalnih rezultata rekonstrukcije prednje ukrštene veze kolena primenom dva tipa suspenzione fiksacije semitendinozus-gracilis grafta na lateralnom femoralnom korteksu

This disertation presents a comparative analysis of results after ALC reconstruction using two implant types for suspensory graft fixation in the femoral tunnel. Injury to the anterior cruciate ligament (ACL) of the knee is the most common ligament injury that requires operative treatment. Patient treatment can be non-operative and operative. So far, multiple ACL reconstruction techniques using a variety of graft types and implants that fixate the grafts have been described. Since 1995, titanium buttons with a loop have been used as implants for suspensory fixation of the graft in the femoral tunnel during ACL reconstruction. There are two types of titanium buttons in use: one with a fixed-length loop and the other with an intraoperative adjustable-length loop. The post-operative knee stability in this disertation was assessed 24 months after surgery using the Lachman test and the lateral pivot shift test, as well as the KT- 1000 arthrometer test. In patients whose graft was fixated using a fixed-length loop implant, the mean post-surgery knee stability, measured with the KT-1000, was 1.27 +/-0.775; in patients whose graft was fixated using an adjustable-length loop implant, the mean value was 1.30+/-1.032 (P=0.691). The mean post-surgery IKDC score for the fixed-length loop group was 85.704 +/-7.792, while for the adjustable-length loop the score was 87.524 +/-6.7708 (P=0.233). The mean Lysholm score was 93.36+/-5.945 for the fixed-length loop group of patients and 92.68 +/-5.266 for the adjustable-length loop group (P=0.395). The mean Cincinnati score for the fixed-length loop group was 90.64 +/-7.030, while for the adjustable-length loop the score was 90.50 +/-8.906 (P=0.846). The mean Single leg hop test was 114.074+/-2.20 for the fixed-length loop and 113.094+/-2.192 for the adjustable length loop group (P=0.5). The results of this study lead to a conclusion that both types of implants can be used with success during ACL reconstruction, because the functional results of operative treatment of ACL reconstruction using both implants were identical after surgery

Gusle, guslarji in njihova društva pri srbskih izseljencih v ZDA

Gusle so glasbeni inštrument, karakterističen za evrazijski prostor. Razširjene so zlasti na dinarskem območju Balkana. V ZDA so jih prinesli srbski izseljenci konec 19. stoletja. Guslarska društva, predvsem tista, katerih člani so bili Črnogorci, so bila na začetku organizirana po vzoru črnogorskih bratstev. Guslarji iz domovine so v času prve svetovne vojne obiskovali srbske kolonije v ZDA in vabili izseljence, naj se pridružijo srbski vojski na Balkanu. V času vojne, ko je bila imigracija omejena, so nekateri ugledni guslarji učiteljevali v župnijskih šolah. Srbski priseljenci v ZDA so po drugi svetovni vojni zastopali raznoliko glasbeno tradicijo. Kljub temu guslanje in guslarji niso bili povsem potisnjeni v ozadje. Pri emigrantih iz Panonije, Like in Bosne je prevladoval glasbeni inštrument - tamburica in drug način petja

Testing the Braneworld Theory with Identical Particles

Various attempts to go beyond the theory of General Relativity start from the assumption that spacetime is not a 4-dimensional but rather a higher-dimensional manifold. Among others, braneworld scenarios postulate that the spacetime we effectively observe is actually a 4-dimensional brane embedded in a higher-dimensional spacetime. In general, braneworld models predict a departure from the Newton gravity law in the nonrelativistic regime. Based on this fact, we propose an experimental test that uses a pair of gravitationally interacting identical particles to determine the validity of certain braneworld models and provide numerical results that should be compared with experimental data. In particular, we consider the Randal-Sundrum braneworld model and study two cases of 5-dimensional gravity theories: the Einstein-Hilbert gravity with the negative cosmological constant and the Einstein-Gauss-Bonnet (nearly-Chern-Simons) gravity.Comment: 6 pages, 6 figures, comments are welcom

Gusle, guslarji in njihova društva pri srbskih izseljencih v ZDA

Gusle is the music instrument which can be found in several regions of Eurasia, but is especially characteristic of Dinaric region in Balkans. At the end of last century, it could have been found in America too. Societies of gusle-players, especially of those originated from Montenegro, at the beginning have been organized on the basis of kin relations. During the First World War, gusle-players from Serbia travelled across USA, visiting Serbian colonies, and calling volunteers to join the army in native country. In the period between world wars, some distinguished gusle-players have been working as teachers in parochial schools. After World War II, Serbian immigrants in USA are represents of various music traditions; among these traditions, gusle-playing is still of certain importance.Gusle so glasbeni inštrument, karakterističen za evrazijski prostor. Razširjene so zlasti na dinarskem območju Balkana. V ZDA so jih prinesli srbski izseljenci konec 19. stoletja. Guslarska društva, predvsem tista, katerih člani so bili Črnogorci, so bila na začetku organizirana po vzoru črnogorskih bratstev. Guslarji iz domovine so v času prve svetovne vojne obiskovali srbske kolonije v ZDA in vabili izseljence, naj se pridružijo srbski vojski na Balkanu. V času vojne, ko je bila imigracija omejena, so nekateri ugledni guslarji učiteljevali v župnijskih šolah. Srbski priseljenci v ZDA so po drugi svetovni vojni zastopali raznoliko glasbeno tradicijo. Kljub temu guslanje in guslarji niso bili povsem potisnjeni v ozadje. Pri emigrantih iz Panonije, Like in Bosne je prevladoval glasbeni inštrument - tamburica in drug način petja

Aspekti merenja brzine vode akustičnom Dopler anemometrijom

The paper analyzes the various aspects of acoustic Doppler anemometry usage, for the measurements of instantaneous water velocity, in the context of the problems of hydraulic engineering. Physical principle of the measuring method is described. The method itself, in current experience, is proved to be extremely robust and practical for the purposes of monitoring, research, etc. Some of the examples of its application both in the laboratory and in field conditions are shown. Practical limitations in the method usage are defined, on the basis of experience in the application. Inherent flaws of the method, which are originating from the use of the Doppler principle for determining speed, are described: Doppler signal aliasing and the appearance of the Doppler noise. Signal aliasing is one of the main problems in the use of this measurement technique, since it affects the accuracy of the measured velocity components. Data contaminated by aliasing errors, can be processed in the post processing by applying some of the algorithms for the detection of peaks and their subsequent replacement. The paper briefly describes the algorithms for the detection of peaks with the use of a filter based on a projection of the phase-space as well as on the basis of correlation between fluctuating velocity components. Also, algorithm for replacement of detected erroneous data using the fitted cubic polynomial interpolation is presented.U radu su analizirani različiti aspekti primene akustične Dopler anemometrije (merenje vektora brzine u jednoj tački) za merenje trenutne brzine vode, u kontekstu problema hidrotehnike. Opisan je fizički princip rada ove merne metode, koja se u dosadašnjem iskustvu pokazala kao izuzetno robusna i praktična za potrebe monitoringa i fundamentalnog istraživanja rasporeda brzina. U radu su prikazani neki od primera njene primene, kako u laboratorijskim tako i u terenskim uslovima. Navedena su i praktična ograničenja upotrebe ove metode, definisana na osnovu iskustva u primeni. Opisane su nasledne mane merne metode koje potiču od upotrebe Doplerovog principa za određivanje brzina: alijasing Doplerovog signala i pojava Doplerovog šuma. Alijasing signala predstavlja jedan od glavnih problema u upotrebi ove merne tehnike, budući da utiče na tačnost proračuna komponenati brzine. Podaci kontaminirani pojavom alijasinga se mogu obraditi u naknadnom procesiranju primenom nekog od algoritama za detekciju pikova i njihovu naknadnu zamenu. U radu su ukratko opisani algoritmi za detekciju pikova sa upotrebom filtra na bazi projekcija faza-prostor kao i na bazi korelacija između fluktuacija komponenata brzina. Takođe, u radu je predložen i algoritam za zamenu detektovanih podataka koji koristi interpolaciju fitovanih kubnih polinoma

Noncommutative SO(2,3)⋆SO(2,3)_{\star} Gauge Theory of Gravity

Topological gravity (in the sense that it is metric-independent) in a $2n$-dimensional spacetime can be formulated as a gauge field theory for the AdS gauge group $SO(2,2n-1)$ by adding a multiplet of scalar fields. These scalars can break the gauge invariance of the topological gravity action, thus making a connection with Einstein's gravity. This review is about a noncommutative (NC) star-product deformation of the four-dimensional AdS gauge theory of gravity, including Dirac spinors and the Yang-Mills field. In general, NC actions can be expanded in powers of the canonical noncommutativity parameter $\theta$ using the Seiberg-Witten map. The leading-order term of the expansion is the classical action, while the higher-order $\theta$-dependent terms are interpreted as new types of coupling between classical fields due to spacetime noncommutativity. We study how these perturbative NC corrections affect the field equations of motion and derive some phenomenological consequences, such as NC-deformed Landau levels of an electron. Finally, we discuss how topological gravity in four dimensions (both classical and noncommutative) appears as a low-energy sector of five-dimensional Chern-Simons gauge theory in the sense of Kaluza-Klein reduction.Comment: 18 pages; Contribution to the special issue of the European Physical Journal on "Noncommutativity and Physics

Prediction of Pest Insect Appearance Using Sensors and Machine Learning

The appearance of pest insects can lead to a loss in yield if farmers do not respond in a timely manner to suppress their spread. Occurrences and numbers of insects can be monitored through insect traps, which include their permanent touring and checking of their condition. Another more efficient way is to set up sensor devices with a camera at the traps that will photograph the traps and forward the images to the Internet, where the pest insect’s appearance will be predicted by image analysis. Weather conditions, temperature and relative humidity are the parameters that affect the appearance of some pests, such as Helicoverpa armigera. This paper presents a model of machine learning that can predict the appearance of insects during a season on a daily basis, taking into account the air temperature and relative humidity. Several machine learning algorithms for classification were applied and their accuracy for the prediction of insect occurrence was presented (up to 76.5%). Since the data used for testing were given in chronological order according to the days when the measurement was performed, the existing model was expanded to take into account the periods of three and five days. The extended method showed better accuracy of prediction and a lower percentage of false detections. In the case of a period of five days, the accuracy of the affected detections was 86.3%, while the percentage of false detections was 11%. The proposed model of machine learning can help farmers to detect the occurrence of pests and save the time and resources needed to check the fields