306 research outputs found
Multi-skyrmion solutions of a sixth order skyrme model
No full textIn this Thesis, we study some of the classical properties of an extension of the Skyrme model defined by adding a sixth order derivative term to the Lagrangian. In chapter 1, we review the physical as well as the mathematical motivation behind the study of the Skyrme model and in chapter 2, we give a brief summary of various extended Skyrme models that have been proposed over the last few years. We then define a new sixth order Skyrme model by introducing a dimensionless parameter λ that denotes the mixing between the two higher order terms, the Skyrme term and the sixth order term. In chapter 3 we compute numerically the multi-skyrmion solutions of this extended model and show that they have the same symmetries with the usual skyrmion solutions. In addition, we analyse the dependence of the energy and radius of these classical solutions with respect to the coupling constant λ. We compare our results with experimental data and determine whether this modified model can provide us with better theoretical predictions than the original one. In chapter 4, we use the rational map ansatz, introduced by Houghton, Manton and Sutcliffe, to approximate minimum energy multi-skyrmion solutions with B ≤ 9 of the SU(2) model and with B ≤ 6 of the SU(3) model. We compare our results with the ones obtained numerically and show that the rational map ansatz works just as well for the generalised model as for the pure Skyrme model, at least for B ≤ 5. In chapter 5, we use a generalisation of the rational map ansatz, introduced by loannidou, Piette and Zakrzewski, to construct analytically some topologically non-trivial solutions of the extended model in SU(3). These solutions are spherically symmetric and some of them can be interpreted as bound states of skyrmions. Finally, we use the same ansatz to construct low energy configurations of the SU(N) sixth order Skyrme model
Matrix quantization of turbulence
No full textBased on our recent work on Quantum Nambu Mechanics [Axenides & Floratos 2009], we provide an explicit quantization of the Lorenz chaotic attractor through the introduction of noncommutative phase space coordinates as Hermitian N × N matrices in R3. For the volume preserving part, they satisfy the commutation relations induced by one of the two Nambu Hamiltonians, the second one generating a unique time evolution. Dissipation is incorporated quantum mechanically in a self-consistent way having the correct classical limit without the introduction of external degrees of freedom. Due to its volume phase space contraction, it violates the quantum commutation relations. We demonstrate that the HeisenbergNambu evolution equations for the Matrix Lorenz system develop fast decoherence to N independent Lorenz attractors. On the other hand, there is a weak dissipation regime, where the quantum mechanical properties of the volume preserving nondissipative sector survive for long times. © 2012 World Scientific Publishing Company
Intraoperative Use of CBCT for Identification and Localization of Calcified Canals: A Clinical Technique
No full textLocalization of calcified canals has always been a challenge in the field of endodontics. The following report of three cases describes a technique for the identification and negotiation of obliterated canals by use of cone beam computed tomography (CBCT) intraoperatively. Canal orifices could not be found clinically in all three cases. Gutta-percha points were placed and compacted at the position where the canal orifices were estimated to be. Intraoperative CBCT was taken, and the distance between the gutta-percha points and the canal orifices was calculated at all planes of space in the first two cases. In the third case, only one canal orifice could be identified due to obliteration of the other canals. © 2017 Spyros Floratos and Maria-Elpida Miltiadous
Complete Set of Unitary Irreps of Discrete Heisenberg Group HW2s
No full textFollowing the method of induced group representations of Wigner-Mackay, the explicit construction of all the unitary irreducible representations of the discrete finite Heisenberg-Weyl group HW2s over the discrete phase space lattice Z2s⊗Z2s is presented. We explicitly determine their characters and their fusion rules. We discuss possible physical applications for finite quantum mechanics and quantum computation. © The Author(s) 2025
The SLiMDisc server: short, linear motif discovery in proteins
No full textShort, linear motifs (SLiMs) play a critical role in many biological processes, particularly in protein-protein interactions. Overrepresentation of convergent occurrences of motifs in proteins with a common attribute (such as similar subcellular location or a shared interaction partner) provides a feasible means to discover novel occurrences computationally. The SLiMDisc (Short, Linear Motif Discovery) web server corrects for common ancestry in describing shared motifs, concentrating on the convergently evolved motifs. The server returns a listing of the most interesting motifs found within unmasked regions, ranked according to an information content-based scoring scheme. It allows interactive input masking, according to various criteria. Scoring allows for evolutionary relationships in the data sets through treatment of BLAST local alignments. Alongside this ranked list, visualizations of the results improve understanding of the context of suggested motifs, helping to identify true motifs of interest. These visualizations include alignments of motif occurrences, alignments of motifs and their homologues and a visual schematic of the top-ranked motifs. Additional options for filtering and/or re-ranking motifs further permit the user to focus on motifs with desired attributes. Returned motifs can also be compared with known SLiMs from the literature. SLiMDisc is available at: http://bioware.ucd.ie/ approximately slimdisc/
Infrared subtraction at next-to-next-to-leading order for gluonic initial states
No full textIn this thesis we describe a procedure for isolating the infrared singularities present in gluonic scattering amplitudes at
next-to-leading and next-to-next-to-leading order. We adopted the
antenna subtraction framework which has been successfully applied to the
calculation of NNLO corrections to the 3-jet cross section and related
event shape distributions in electron-positron annihilation. We consider
processes with coloured particles in the initial state, and in
particular two-jet production in hadron-hadron collisions at
accelerators such as the Large Hadron Collider (LHC). We derive explicit
formulae for subtracting the single and double unresolved contributions
from the double radiation gluonic processes using
antenna functions with initial state partons. We show numerically that
the subtraction term effectively approximates the matrix element in the
various single and double unresolved configurations
Complete set of unitary irreps of Discrete Heisenberg Group
No full textFollowing the method of induced group representations of Wigner-Mackay, the
explicit construction of all the unitary irreducible representations of the
discrete finite Heisenberg-Weyl group over the discrete phase space
lattice is presented. We explicitly determine
their characters and their fusion rules. We discuss possible physical
applications for finite quantum mechanics and quantum computation.Comment: 25 page
Checking consistency and completeness of production rules
No full textThis thesis was scanned from the print manuscript for digital preservation and is copyright the author.
Researchers can access this thesis by asking their local university, institution or public library to
make a request on their behalf. Monash staff and postgraduate students can use the link in the References field
The quantum cat map on the modular discretization of extremal black hole horizons
No full textBased on our recent work on the discretization of the radial AdS 2 geometry of extremal BH horizons, we present a toy model for the chaotic unitary evolution of infalling single-particle wave packets. We construct explicitly the eigenstates and eigenvalues for the single-particle dynamics for an observer falling into the BH horizon, with as time evolution operator the quantum Arnol’d cat map (QACM). Using these results we investigate the validity of the eigenstate thermalization hypothesis (ETH), as well as that of the fast scrambling time bound (STB). We find that the QACM, while possessing a linear spectrum, has eigenstates, which are random and satisfy the assumptions of the ETH. We also find that the thermalization of infalling wave packets in this particular model is exponentially fast, thereby saturating the STB, under the constraint that the finite dimension of the single-particle Hilbert space takes values in the set of Fibonacci integers. © 2018, The Author(s)
Large-spin expansions of GKP strings
No full textWe demonstrate that the large-spin expansion of the energy of Gubser-Klebanov-Polyakov (GKP) strings that rotate in ℝ × S 2 and AdS3 can be expressed in terms of Lambert's W-function. We compute the leading, subleading and next-to-subleading series of exponential corrections to the infinite-volume dispersion relation of GKP strings that rotate in ℝ × S2. These strings are dual to the long N = 4 SYM operators Tr[ΦZmΦZJ-m]+. and provide their scaling dimensions at strong coupling. We also show that the strings obey a short-long (strings) duality. For the folded GKP strings that spin inside AdS3 and are dual to twist-2 operators, we confirm the known formulas for the leading and next-to-leading coefficients of their anomalous dimensions and derive the corresponding expressions for the next-to-next-to-leading coefficients. © 2014 The Author(s)
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