Results 1 - 10 of 4812
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[en] For conceptual reasons we consider off-mass shell second quantized states. The physical states are recovered by a generalized eigenvalues system of equations. This is explicitly shown for scalar free particles. In view of constructing interactions we introduce an off-shell field operator
[fr]On considere, a titre conceptuel, des etats superquantifies qui sont en dehors de la couche de masse. Les etats physiques sont recuperes au moyen d'un systeme d'equations aux valeurs propres generalisees. On le montre explicitement pour des particules scalaires libres. Dans le but de construire ensuite des interactions, on introduit un operateur de champ hors-couche
[en] We present exact formulas for the form factors of local operators in the repulsive Lieb–Liniger model at finite size. These are essential ingredients for both numerical and analytical calculations. From the theory of algebraic Bethe ansatz, it is known that the form factors of local operators satisfy a particular type of recursive relations. We show that in some cases these relations can be used directly to derive practical expressions in terms of the determinant of a matrix whose dimension scales linearly with the system size. Our main results are determinant formulas for the form factors of the operators and ΨR(0), for arbitrary integer R, where Ψ, are the usual field operators. From these expressions, we also derive the infinite size limit of the form factors of these local operators in the attractive regime. (paper)
[en] Recent developments for BPHZ renormalization performed in configuration space are reviewed and applied to the model of a scalar quantum field with quartic self-interaction. An extension of the results regarding the short-distance expansion and the Zimmermann identity is shown for a normal product, which is quadratic in the field operator. The realization of the equation of motion is computed for the interacting field and the relation to parametric differential equations is indicated.
[en] The representations of the basic real tensor sup(*)gsup(lambdaμ) in sup(*)g-unified field theory have been obtained in various forms for the lower dimensional cases mainly by Hlavaty and one of the authors. Recently, n-dimensional representations of the tensor fields sup(*)gsup(lambdaμ) were obtained in 6) and 9). They look quite different in their forms even though they are identical. In the present paper, we prove that these different representations are equivalent in the lower dimensional cases, using the corresponding recurrence relations. (Author)
[en] We analyze an ambiguity in previous works on entanglement of fermionic fields in noninertial frames. This ambiguity, related to the anticommutation properties of field operators, leads to nonunique results when computing entanglement measures for the same state. We show that the ambiguity disappears when we introduce detectors, which are in any case necessary as a means to probe the field entanglement.
[en] A scheme is proposed for including electromagnetic interaction into the theories of stretched relativistic objects. In the theory of the straight string, the operator of electromagnetic interaction is constructed, and form factors of electromagnetic transitions are calculated. 6 refs., 1 fig
[en] Within the context of piecewise linear manifolds we establish reflection positivity with a Hilbert action given in terms of the Regge curvature and a cosmological term. Using this positivity a Hilbert space for a quantum theory is constructed and some field operators and observables are given. The set-up allows to introduce time reversal though no time exists. All constructions are non-perturbative. (paper)
[en] We show that unstable D-branes play the role of ''D-sphalerons'' in string theory. Their existence implies that the configuration space of Type II string theory has a complicated homotopy structure, similar to that of an infinite Grassmannian. In particular, the configuration space of Type IIA (IIB) string theory on R10 has non-trivial homotopy groups πk for all k even (odd). (author)