433 research outputs found
Dynamics of self-interacting strings and energy-momentum conservation
No full textClassical strings coupled to a metric, a dilaton and an axion, as
conceived by superstring theory, suffer from ultraviolet divergences
due to self-interactions. Consequently, as in the case of
radiating charged particles, the corresponding effective string dynamics
cannot be derived from an action principle. We propose a
fundamental principle to build this dynamics, based on local energymomentum
conservation in terms of a well-defined
distribution-valued energy-momentum tensor. Its continuity
equation implies a finite equation of motion for self-interacting
strings. The construction is carried out explicitly for strings in
uniform motion in arbitrary space–time dimensions, where we
establish cancelations of ultraviolet divergences which parallel
superstring non-renormalization theorems. The uniqueness properties
of the resulting dynamics are analyzed
Classical Electrodynamics - A Modern Perspective
No full textThis book addresses the theoretical foundations and the main physical consequences of electromagnetic interaction, generally considered to be one of the four fundamental interactions in nature, in a mathematically rigorous yet straightforward way. The major focus is on the unifying features shared by classical electrodynamics and all other fundamental relativistic classical field theories. The book presents a balanced blend of derivations of phenomenological predictions from first principles on the one hand, and concrete applications on the other. Further, it highlights the internal inconsistencies of classical electrodynamics, and addresses and resolves often-ignored critical issues, such as the dynamics of massless charged particles, the infinite energy of the electromagnetic field, and the limits of the Green’s function method. Presenting a rich, multilayered, and critical exposition on the electromagnetic paradigm underlying the whole Universe, the book offers a valuable resource for researchers and graduate students in theoretical physics alike
String κ-anomalies and D = 10 supergravity constraints: the solution of a puzzle
No full textThe κ-anomaly cancellation mechanism in the heterotic superstring determines the superspace constraints for N = 1, D = 10 Supergravity-Super-Yang-Mills theory. We point out that the constraints found recently in this way appear to disagree with superspace solutions found in the past. We solve this puzzle establishing perfect agreement between the two methods. © 1995
Elettrodinamica classica: teoria e applicazioni
No full textIl libro è un testo di Elettrodinamica classica avanzata e comprende anche le basi della Teoria dei campi classici. Come tale è rivolto a qualsiasi studente o ricercatore di Fisica Teorica. Una caratteristica fondamentale del testo è rappresentata da una derivazione rigorosa dei fenomeni ettromagnetici dalle fondamenta teorico-matematiche della teoria, che mette bene in evidenze le inconsistenze e i limiti interni della teoria. Il testo contiene anche un certo numero di argomenti recenti o speculativi che nei libri di testo vengono affrontati solo superficialmente
Radiation reaction and 4-momentum conservation for point-like dyons
No full textWe construct for a system of point-like dyons a conserved energy-momentum tensor entailing finite momentum integrals, that takes the radiation reaction into account
Intersecting M2- and M5-branes
No full textIf an M2-brane intersects an M5-brane the canonical Wess-Zumino action is plagued by a Dirac-anomaly, i.e. a non-integer change of the action under a change of Dirac-brane. We show that this anomaly can be eliminated at the expense of a gravitational anomaly supported on the intersection manifold. Eventually we check that the last one is cancelled by the anomaly produced by the fermions present. This provides a quantum consistency check of these intersecting configurations
4-GRAVITON SCATTERING IN D = 4 SUPERSTRINGS WITH BROKEN SPACE-TIME SUPERSYMMETRY
No full textWe construct the one-loop four-graviton amplitude in a four-dimensional type II superstring model with broken (N = 4) space-time SUSY. The amplitude is seen to be a sum of the amplitude with unbroken highest N = 8 SUSY, A8, plus a term A4 which breaks SUSY down to N = 4. The new term A4 is seen to contain rescattering diagrams, which are also present in A8, and to open one-particle-reducible channels containing gravitons, due to the absence of non-renormalization theorems for it. The evaluation of the contributions to the amplitude of these channels in the limit of large external energies and of small momentum transfer confirms that the effective metric due to a graviton source is not of the classical Schwarzschild-type, not even at broken SUSY. Moreover, we check that, in spite of the absence of non-renormalization theorems, the graviton mass and wave function are not renormalized. We find infrared singularities in A4, which are not present in A8, individuate their nature and guess a ..
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