Giant Holes

We study the semiclassical spectrum of excitations around a long spinning string in AdS_3. In addition to the usual small fluctuations, we find the spectrum contains a branch of solitonic excitations of finite energy. We determine the dispersion relation for these excitations. This has a relativistic form at low energies but also matches the dispersion relation for the "hole" of the dual gauge theory spin chain at high energies. The low-energy behaviour is consistent with the hypothesis that the solitonic excitations studied here are continuously related to the elementary excitations of the string.Comment: 17 pages, 1 figure; additional references include

Caleidoscopi; Allora la luna

Il progetto nasce dalla committenza di Roberto Daolio per la realizzazione di opere da collocare all’ultimo piano del reparto di Oncologia Pediatrica dell’Ospedale Sant’Orsola di Bologna in collaborazione con l’Associazione Ageop. Gli artisti invitati sono Silvia Cini, Emilio Fantin, Claudia Losi, Eva Marisaldi, Sabrina Mezzaqui, Sabrina Torelli e Marco Vaglieri. Per il reparto Losi immagina due progetti: Caleidoscopi, prismi colorati con cui giocare racchiusi i astucci di balsa e Allora la luna, una sorta di insegna luminosa del diametro di due metri circa pensata per una installazione esterna, su uno dei corpi architettonici sui quale si affacciavano le finestre del reparto: entrambi i progetti sono pensati per stimolare l’immaginazione dei piccoli pazienti e per permettere loro di distrarsi dalla loro condizione. Il progetto non viene realizzato a seguito di una serie di motivazioni economiche, tecnico logistiche.The project was commissioned by Roberto Daolio as part of a series of art works to be placed on the top floor of the Department of Pediatric Oncology of the Sant’Orsola Hospital in Bologna, in collaboration with the Association AGEOP. The invited artists are Silvia Cini, Emilio Fantin, Claudia Losi, Eva Marisaldi, Sabrina Mezzaqui, Sabrina Torelli and Marco Vaglieri. For the Hospital department Losi imagined two projects: Caleidoscopi (Kaleidoscopes), colored prisms to play with, enclosed in balsa wood cases, and Allora la luna (Then the moon), a sort of luminous sign with a diameter of about two meters designed for outdoor installation, to be placed on one of the buildings in front of the windows of department: both projects were meant to stimulate the imagination of young patients and to allow them to forget their condition for a moment. The project was not realized as a result of a number of economical, technical and logistic reasons. See interview with Francesca Testoni, Responsible for assistance. A.G.E.O.

Spiky strings and the AdS/CFT correspondence

In this dissertation, we explore some aspects of semiclassical type IIB string theory on AdS3 × S1 and on pure AdS3 in the limit of large angular momentum S. We first focus on the integrability technique known as finite-gap formalism for strings in AdS3 × S1, leading to the definition of a hyperelliptic Riemann surface, the spectral curve, which encodes, albeit in a rather implicit fashion, the semiclassical spectrum of a very large family of string solutions. Then, we show that, in the large angular momentum limit, the spectral curve separates into two distinct surfaces, allowing the derivation of an explicit expression for the spectrum, which is correspondingly characterised by two separate branches. The latter may be interpreted in terms of two kinds of spikes appearing on the strings: “large” spikes, yielding an infinite contribution to the energy and angular momentum of the string, and “small” spikes, representing finite excitations over the background of the “large” spikes. According to the AdS/CFT correspondence, strings moving in AdS3 × S1 should be dual to single trace operators in the sl(2) sector of N = 4 super Yang- Mills theory. The corresponding one-loop spectrum in perturbation theory may also be computed through integrability methods and, in the large conformal spin limit S → ∞ (equivalent to the AdS3 angular momentum in string theory) is also expressed in terms of a spectral curve and characterised in terms of the so-called holes. We show that, with the appropriate identifications and with the usual extrapolation from weak to strong ’t Hooft coupling described by the cusp anomalous dimension, the large-S spectra of gauge theory and of string theory coincide. Furthermore, we explain how “small” and “large” holes may be identified with “small” and “large” spikes. Finally, we discuss several explicit spiky string solutions in AdS3 which, at the leading semiclassical order, display the previously studied finite-gap spectrum. We compute the spectral curves of these strings in the large S limit, finding that they correspond to specific regions of the moduli space of the finite-gap curves. We also explain how “large” spikes may be used in order to extract a discrete system of degrees of freedom from string theory, which can then be matched with the degrees of freedom of the dual gauge theory operators, and how “small” spikes are in fact very similar to the Giant Magnons living in R × S2.Domestic Research Scholarship (fees only); Cambridge European Trust and Isaac Newton Trust (Isaac Newton Trust European Research Studentship)

Neurological deterioration in American football players

Neurodegenerative diseases are believed to occur at an increased rate for those who participate in contact sports. More recent attention has been given to players of the National Football League after it was proposed that they are at an increased risk of developing neurodegenerative diseases including chronic traumatic encephalopathy (CTE), Parkinson’s Disease (PD), Amyotrophic Lateral Sclerosis (ALS), and Alzheimer’s Disease (AD). Though multiple studies have found a correlation between concussive and sub-concussive events and the development of CTE, the validity of these is being questioned. Many of the brain specimens available to evaluate have been samples of convenience or were donated by concerned family members of those who were displaying signs of neurodegenerative diseases potentially biasing the results. Additionally, recall bias is a concern in some studies due to athletes or family members of athletes giving histories of concussive or sub-concussive events many years after players had retired. Current evidence regarding neurodegenerative diseases, including CTE, and their development in NFL players is not sufficient to make concrete conclusions. It has become clear that more information regarding CTE and its progression needs to be gathered. The proposed study extends the analysis originally completed by Lehman et. al to determine if there is an increased risk of developing neurodegenerative diseases in NFL players who have played at least five seasons when compared to the general population. Investigators will use the Life Table Analysis System (LTAS.NET) from the Center for Disease Control and Prevention (CDC) to analyze this cohort. It is impossible to investigate CTE as a cause of death directly; it has only recently been studied and will, therefore, not be found on death certificates as a listed cause of death. Thus, this study will use other neurodegenerative diseases (PD, ALS, AD) as a possible marker for CTE

Structured light assisted real-time stereo photogrammetry for robotics and automation. Novel implementation of stereo matching

In this Master’s thesis project a novel implementation of a stereo matching based method is proposed. Moreover, an exhaustive analysis of the state-of-the-art algorithms in that field is outlined. Specifically, both standard and deep learning based methods have been extensively investigated, thus to provide useful insights for the designed implementation. Regarding the developed work, it is basically structured in the following manner. At first a research phase has been carried out, hence to simply and rapidly test the thought strategy. Subsequently, a first implementation of the algorithm has been designed and tested using data available from the Middlebury 2014 dataset, which is one of the most exploited dataset in the computer vision area. At this stage, numerous tests have been completed and consequently various changes to the algorithm pipeline have been made, in order to improve the final result. Finally, after that exhaustive researching phase the actual method has been designed and tested using real environment images obtained from the stereo device developed by the company, in which this work has been produced. Fundamental element of the project is indeed that stereo device. As a matter of fact, the designed algorithm in based on the data produced by the cameras that constitute it. Specifically, the main function of the system designed by LaDiMo is to make the built stereo matching based procedure simultaneously faster and accurate. As a matter of fact one of the main prerogative of the project was to create an algorithm that has to prove potential real-time results. This has been in fact, achieved by applying one of the two methods created. Specifically, it is a lightweight implementation, which strongly exploits the information coming from the LaDiMo device, thus to provide accurate results, keeping the computational time short. At the end of this Master’s thesis images showing the main outcomes obtained are proposed. Moreover, a discussion regarding the further improvements that are going to be added to the project is stated. In fact, the method implemented, being not optimized only demonstrate a potential real-time implementation, which would be certainly achieved through an efficient refactoring of the main pipeline

Political ethics from an Islamic perspective

Political ethics laid the foundations of the fundamental human beings as humans, and it is, in fact, human individuals and society members. Men are civilized and cultured, and they do not live outside certain cultures and etiquette. Politically inextricably linked with the thinkers of Islam, politically indivisible. The difference is that when Greek thinkers discuss the interconnectedness of it in the realm of moral philosophy, Islamic political thinkers discuss it within the auspices of theology. This is a sign indicating that the issue of political Islam does not separate the argument with religion

Thyroid hormones modulate GABA(A) receptor-mediated currents in hippocampal neurons( 2011) .

Thyroid hormones (THs) play a crucial role in the maturation and functioning of mammalian central nervous system. Thyroxine (T4) and 3, 3', 5-L-triiodothyronine (T3) are well known for their genomic effects, but recently attention has been focused on their non genomic actions as modulators of neuronal activity. In the present study we report that T4 and T3 reduce, in a non competitive manner, GABA-evoked currents in rat hippocampal cultures with IC₅₀s of 13±4μM and 12±3μM, respectively. The genomically inactive compound rev-T3 was also able to inhibit the currents elicited by GABA. Blocking PKC or PKA activity, chelating intracellular calcium, or antagonizing the integrin receptor αVβ3 with TETRAC did not affect THs modulation of GABA-evoked currents. THs affect also synaptic activity in hippocampal and cortical cultured neurons. T3 and T4 reduced to approximately 50% the amplitude and frequency of spontaneous inhibitory synaptic currents (sIPSCs), without altering their decay kinetic. Tonic currents evoked by low GABA concentrations were also reduced by T3 (40±5%, n=14), but not by T4. Similarly, T3 decreased currents elicited by low concentrations of THIP, a low affinity GABAA receptor agonist that preferentially activates extrasynaptic receptors, whereas T4 was ineffective. Thus, our data demonstrate that T3 and T4 selectively affect GABAergic phasic and tonic neurotransmission. Since THs concentrations can be regulated at the level of the synapses these data suggest that the network activity of the whole brain could be differently modulated depending on the relative amount of these two hormones