Thesis (Ph.D.)--Boston University / PLEASE NOTE: Boston University Libraries did not receive an Authorization To Manage form for this thesis or dissertation. It is therefore not openly accessible, though it may be available by request. If you are the author or principal advisor of this work and would like to request open access for it, please contact us at open-help@bu.edu. Thank you. / The principal purpose of this thesis was to calculate certain mass differences of elementary particles in second order perturbation theory, within the framework of a gauge invariant theory of interactions. First we calculated the mass difference of the electron and the muon on the assumption that they have same bare mass and have different physical masses as a result of their interaction with a neutral vector meson field whose quantum is the phi meson. The previous attempts in this direction treated the muon and the electron unsymmetrically, which caused the ratio of the pion decay into (electron + electronic neutrino) to the pion decay into (muon + muonic neutrino) to have a value not permitted by the accuracy of the experimental results. Those calculations predicted also the value of the anomalous magnetic moment of the muon much higher than the experimental value. Our calculation, on the other hand, not only gives the mass difference of the muon and the electron in agreement with their experimental value but also does not run into any difficulty faced by the previous calculations. Secondly, generalizing the meaning of the electromagnetic interaction, we calculated the mass differences of the different members of every charge multiplet of the strongly interacting particles. Only with two adjustable parameters we have been able to predict the mass differences of the seven pairs of particles. Finally, we speculated on the origin of the masses of the phi and rho mesons. Using the coupling constants previously introduced, we calculated their masses in agreement with the experimental masses. We used the same cut-off parameter as was assumed for the electromagnetic mass splitting. / 2031-01-01

The gauge-invariant formulation of quantum mechanics is compared to the conventional approach for the case of a one-dimensional charged harmonic oscillator in an electromagnetic field in the electric dipole approximation. The probability of finding the oscillator in the ground state or excited states as a function of time is calculated, and the two approaches give different results. On the basis of gauge invariance, the gauge-invariant formulation of quantum mechanics gives the correct probability, while the conventional approach is incorrect for this problem. Therefore, expansion coefficients or a wave function cannot always be interpreted as probability amplitudes. For a physical interpretation as probability amplitudes the expansion coefficients must be gauge invariant.

Quantum Chromo Dynamics (QCD) is a relativistic field theory of a non-abelian gauge field coupled to several flavors of fermions. Two dimensional (one space and one time) QCD serves as an interesting toy model that shares several features with the four dimensional physically relevant theory. The main aim of the research is to study two dimensional QCD using the lattice regularization. Two dimensional QCD without any fermion content is solved analytically using lattice regularization. Explicit expressions for the expectation values of Wilson loops and the correlation of two Polyakov loops oriented in two different directions are obtained. Physics of the QCD vacuum is explained using these results. The Hamiltonian formalism of lattice QCD with fermion content serves as an approach to study quark excitations out of the vacuum. The formalism is first developed and techniques to numerically evaluate the spectrum of physical particles, namely, meson and baryons are described. The Hybrid Monte Carlo technique was used to numerically extract the lowest meson and baryon masses as a function of the quark masses. It is shown that neither the lowest meson mass nor the lowest baryon mass goes to zero as the quark mass is taken to zero. This numerically establishes the presence of a mass gap in two dimensional QCD.

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Orientador: Vicente Pleitez / Mestre

ITC/USA 2005 Conference Proceedings / The Forty-First Annual International Telemetering Conference and Technical Exhibition / October 24-27, 2005 / Riviera Hotel & Convention Center, Las Vegas, Nevada / For years, ballisticians have been studying the phenomena associated with cannon launched projectiles. In particular, is the study of the pressure internal to the cannon and about the base of the projectile during cannon launch through muzzle exit. Pressure on the base is thought to be uniform and therefore hydrostatic, even though there are undulations in the magnitude of the pressure from the burning propellant. This paper studies various phenomena of the launching of 155-mm artillery projectiles with slip band obturators. Specifically, pressure gradients in and around the base and pressure along the body caused by obturator “blow-by” during the interior ballistic flight and muzzle exit. This study is accomplished by use of two different types of Instrumented Ballistic Test Projectiles (IBTP). The objective of tests performed was to successfully capture pressure and acceleration live data which will be used to characterize the localized base and body pressurization on a 155-mm artillery cannon launched projectile. The telemetry system used for these tests was the ARRT-124 telemetry system provided by the Armament Research, Development, and Engineering Center, specifically the Precision Munitions Instrumentation Division. The telemetry system used for the IBTP employs a traditional FM/FM technique for monitoring and transmitting a number of analog channels. Preliminary captured data indicated localized fluctuations in pressure that are not uniform over the base and the projectile body. Further studying of the data may provide insight into other projectile dynamics such as fin deployment, set forward accelerations at muzzle exit, and obturator performance.

Cette thèse s'inscrit dans le cadre de la physique mathématique des interactions fondamentales. Elle porte sur l'étude des théories de champs qui décrivent les particules élémentaires. En particulier, les théories de champs de spin élevé (plus grand ou égal à 2) sont analysées. Mis à part pour le graviton, vecteur supposé des interactions gravitationnelles, il n'y a aucun indice que ces champs soient présents dans la nature. Cependant leur existence n'est pas impossible théoriquemement et ils interviennent dans la théorie des cordes, candidate pour une théorie quantique d'unification de toutes les forces fondamentales y compris la gravitation. En effet, les modes de vibration de la corde élémentaire sont décrits par des champs de spin élevé.   Dans ce travail, la dimension de l'espace-temps est laissée arbitraire, ce qui entraine la possibilité d'avoir plusieurs sortes (= représentations) de champs différentes ayant le même spin. Le premier aspect traité dans cette thèse concerne les dualités, symétries qui relient entre elles plusieurs théories. Il est montré que différentes représentations de champs de spin élevé sont duales au niveau de l'action. En particulier, en dimension quatre, la dualité échange la composante électrique et la composante magnétique d'un même champs. Cette propriété est ensuite utilisée pour introduire des sources magnétiques pour les champs de spin élevé. La construction généralise les travaux de Dirac sur le couplage au champ électromagnétique de monopoles magnétiques. Une condition de quantification est également dérivée pour des quantités conservées, qui généralise la condition de quantification de Dirac pour la charge électrique en présence de monopoles magnétiques. La deuxième partie de la thèse est consacrée aux interactions de champs de spin élevé. L'analyse est effectuée dans le formalisme de champs et d'antichamps dévelopé par Batalin et Vilkovsky. Elle repose sur la procédure de déformation de l'équation maîtresse mise au point par Henneaux et Barnich. Les champs étudiés sont les champs de spin deux exotiques (c-à-d différents du graviton) ainsi que les champs de spin trois complètement symétriques. Pour les premiers, il est prouvé que toutes les interactions doivent être abélienne. Il n'y a donc pas d'équivalent de la théorie d'Einstein pour ces champs. Dans le cas des champs de spin trois, plusieurs vertex cohérents au premier ordre sont obtenus. <br> In this thesis, we consider two aspects of higher-spin gauge field theories: dualities and interactions. The first aspect is related to the presence of dualities, i.e., 'hidden' symmetries among gauge field theories. Do two higher-spin theories corresponding to different irreducible representations of the Poincaré group have the same physical content. Duality relations were already known at the level of the equations of motion and Bianchi identities, here we prove (in some cases) that these dualities hold also at the level of the action. As a consequence, the dual theories are formally equivalent. For example, in five space-time dimensions the spin-two theory of Pauli and Fierz is dual to the theory of a mixed-symmetry spin-two field written by Curtright. In four space-time dimensions the duality exchanges the electric and magnetic degrees of freedom of the field. This property leads us to introduce external magnetic sources for higher-spin fields, thereby generalizing to arbitrary spin the work of Dirac on the coupling of magnetic monopoles to the electromagnetic field. Similarly to the quantization condition on the product of the electric and magnetic charges for electromagnetism, there is a quantization condition on the product of conserved ``electric' and ``magnetic' charges for higher spins. The second aspect of higher-spin gauge field theories that is analysed in this thesis is the problem of interactions. Self-interactions of exotic spin-two gauge fields are studied, as well as self-interactions of completely symmetric spin-three fields. This is done in the BRST field-antifield formalism developped by Batalin and Vilkovisky, using the technique of consistent deformations of the master equation proposed by Barnich and Henneaux.

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