Results 1 - 10 of 29070
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[en] A scalar field theory with a χ†χφ interaction is known to be unstable. Yet it has been used frequently without any sign of instability in standard textbook examples and research articles. In order to reconcile these seemingly conflicting results, we show that the theory is stable if the Fock space of all intermediate states is limited to a finite number of closed χ bar χ loops associated with a field χ that appears quadradically in the interaction, and that instability arises only when intermediate states include these loops to all orders. In particular, the quenched approximation is stable
[en] First, recent work on light scalar mesons, which is of possible interest in connectionwith the strong coupling region of QCD, is briefly discussed. Then a very shorthighlighting of a paper concerned with an application to the eta --> 3pi problem ispresented.
[en] The back-reaction on the Randall-Sundrum warped spacetime is determined in the presence of a scalar field in the bulk. A general condition for the stability of such a model is derived for a bulk scalar field action with non-canonical higher derivative terms. It is further shown that the gauge hierarchy problem can be resolved in such a stabilized scenario by appropriate choice of various parameters of the theory.
[en] Gradient networks are defined (Toroczkai and Bassler 2004 Nature 428 716) as directed graphs formed by local gradients of a scalar field distributed on the nodes of a substrate network G. We present the derivation for some of the general properties of gradient graphs and give an exact expression for the in-degree distribution R(l) of the gradient network when the substrate is a binomial (Erdos-Renyi) random graph, GN,p, and the scalars are independent identically distributed (i.i.d.) random variables. We show that in the limit N→∞, p→0, z=pN=const>>1, R(l)∝l-1 for lc=z, i.e., gradient networks become scale-free graphs up to a cut-off degree. This paper presents the detailed derivation of the results announced in Toroczkai and Bassler (2004 Nature 428 716)
[en] We present the explicit construction of some multi-scalar field theories in (1+1) dimensions supporting BPS (Bogomol’nyi–Prasad–Sommerfield) kink solutions. The construction is based on the ideas of the so-called extension method. In particular, several new interesting two-scalar and three-scalar field theories are explicitly constructed from non-trivial couplings between well-known one-scalar field theories. The BPS solutions of the original one-field systems will be also BPS solutions of the multi-scalar system by construction, and therefore we will analyse their linear stability properties for the constructed models.
[en] The classical and quantum correlation sharing between modes of Dirac fields in the noninertial frame are investigated. It is shown that (i) the classical correlation for the Dirac fields decreases as the acceleration increases, which is different from the result in a scalar field, where the classical correlation is independent of the acceleration; (ii) there is no simple dominating relation between the quantum correlation and entanglement for the Dirac fields, which is unlike the scalar case, where the quantum correlation is always over and above the entanglement; (iii) as the acceleration increases, the correlations between modes I and II and between modes A and II increase, but the correlations between modes A and I decrease.
[en] We study the scattering of low-energy massless and massive minimally coupled scalar fields by an asymptotically flat traversable wormhole. We provide a comprehensive treatment of this problem offering analytic expressions for the transmission and reflection amplitudes of the corresponding effective potential and the absorption cross section of the wormhole. Our results, which are based on a recently developed dynamical formulation of time-independent scattering theory, apply to a large class of wormhole spacetimes including a wormhole with a sharp transition, the Ellis wormhole, and a family of its generalizations.
[en] We calculate the mass shifts of heavy-light scalar mesons due to hadronic loops under the assumption that these vanish for the groundstate heavy-light mesons. The results show that the masses calculated in quark models can be reduced significantly. We stress that the mass alone is not a signal for a molecular interpretation. Both the resulting mass and the width suggest the observed D0* state could be a dressed cq-bar state. We give further predictions for the bottom scalar mesons which can be used to test the dressing mechanism
[en] It is shown that a sufficient condition for Birkhoff's (Birkhoff, G.D., Relativity and Modern Physics, Harvard University Press (1927)) theorem to hold for the Sen-Dunn (Sen, D.K.; Dunn, K.A., J. Math. Phys.; 12:578 (1971)) and Ross (Ross, D.K., Phys. Rev.; D5:284 (1972)) scalar-tensor theories of gravitation is that the scalar field should be time-invariant. An earlier result due to Reddy (Reddy, D.R.K., J. Phys. A; 6:1867 (1973)) in the case of the Sen-Dunn theory is thus corrected. (U.K.)