Bohmian trajectories for photons
The first examples of Bohmian trajectories for photons have been worked out for simple situations, using the Kemmer-Duffin-Harishchandra formalism.
quant-ph↗
arXiv subjects
A. S. Majumdar
Publications and source records attributed to A. S. Majumdar.
Quantum Supearrivals
A curious effect is uncovered by calculating the it time evolving probability of reflection of a Gaussian wave packet from a rectangular potential barrier while it is perturbed by reducing its height. A time interval is found during which this probability of reflection is larger (``superarrivals'') than in the unperturbed case. This nonclassical effect can be explained by requiring a wave function to act as a ``field'' through which an action, induced by the perturbation of the boundary condition, propagates at a speed depending upon the rate of reducing the barrier height.
quant-ph↗
From brane assisted inflation to quintessence through a single scalar field
We explore within the context of brane cosmology whether it is possible to obtain both early inflation and accelerated expansion during the present epoch through the dynamics of the same scalar field in an exponential potential. Considerations from successful inflation and viable radiation and matter dominated eras impose constraints on the parameters of the potential. We find that the additional requirement of late time quintessence behaviour in conformity with present observations necessitates the inclusion of two exponential terms in the potential.
astro-ph↗
Aspects of nonlocality in atom-photon interactions in a cavity
We investigate a Bell-type inequality for probabilities of detected atoms formulated using atom-photon interactions in a cavity. We consider decoherence brought about by both atomic decay, as well as cavity photon loss, and study its quantitative action in diminishing the atom-field and the resultant atom-atom secondary correlations. We show that the effects of decoherence on nonlocality can be observed in a controlled manner in actual experiments involving the micromaser and also the microlaser.
quant-ph↗
Interpreting the time of decay measurement: phenomenological significance of the Bohm model
We point out that the spreading of wave packets could be significant in affecting the analysis of experiments involving the measurement of time of decay. In particular, we discuss a hitherto unexplored application of the Bohm model in properly taking into account the nontrivial effect of wave packet spreading in the CP violation experiment.
quant-ph↗
Effects of Dicke superradiance in context of the one-atom maser
We consider a micromaser model to study the influence of Dicke superradiance in the context of the one-atom maser. The model involves a microwave cavity into which two-level Rydberg atoms are pumped in pairs. We consider a random pump mechanism which allows the presence of at most one pair of atoms in the cavity at any time. We analyze the differences between the present system, called the Dicke micromaser, and an equivalently pumped conventional one-atom micromaser. These differences are attributed to the Dicke cooperativity in the two-atom system. We also show that the two-atom Dicke micromaser is equivalent to a one-atom cascade two-photon micromaser. With the introduction of a one-photon detuning, the present theory further describes a true two-photon micromaser. We discuss in detail the role of one-photon detuning in the mechanism of a one-atom two-photon micromaser. This leads us to point out that the two-atom cavity dynamics can be verified by a proper scaling of the results from an equivalent one-atom two-photon micromaser.
quant-ph↗
Inflationary universe in Kaluza-Klein theories
We describe extended inflation and its typical problems. We then briefly review essential features of Kaluza-Klein theory, and show that it leads to a scenario of inflationary cosmology in four dimensions. The problem of stable compactification of extra spatial dimensions is discussed. The requirements for successful extended inflation lead to constraints on the parameters of higher dimensional models.
astro-ph↗
Solitons in a gauged Landau-Lifshitz model
We study the gauged Landau-Lifshitz model in which a suitably chosen triplet of background scalar fields is included. It is shown that the model admits solitonic configurations.
hep-th↗
On the importance of the Bohmian approach for interpreting CP-violation experiments
We argue that the inference of CP violation in experiments involving the $K^0-\bar{K^0}$ system in weak interactions of particle physics is facilitated by the assumption of particle trajectories for the decaying particles and the decay products. A consistent explanation in terms of such trajectories is naturally incorporated within the Bohmian interpretation of quantum mechanics.
quant-ph↗
Hamiltonian Analysis of Gauged $CP^1$ Model, the Hopf term, and fractional spin
Recently it was shown by Cho and Kimm that the gauged $CP^1$ model, obtained by gauging the global $SU(2)$ group and adding a corresponding Chern-Simons term, has got its own soliton. These solitons are somewhat distinct from those of pure $CP^1$ model as they cannot always be characterised by $π_2(CP^1)=Z$. In this paper, we first carry out a detailed Hamiltonian analysis of this gauged $CP^1$ model. This reveals that the model has only $SU(2)$ as the gauge invariance, rather than $SU(2) \times U(1)$. The $U(1)$ gauge invariance of the original (ungauged) $CP^1$ model is actually contained in the $SU(2)$ group itself. Then we couple the Hopf term associated to these solitons and again carry out its Hamiltonian analysis. The symplectic structures, along with the structures of the constraints of these two models (with or without Hopf term) are found to be essentially the same. The model with a Hopf term is shown to have fractional spin which, when computed in the radiation gauge, is found to depend not only on the soliton number $N$, but also on the nonabelian charge. We then carry out a reduced (partially) phase space analysis in a different physical sector of the model where the degrees of freedom associated with the $CP^1$ fields are transformed away. The model now reduces to a $U(1)$ gauge theory with two Chern-Simons gauge fields getting mass-like terms and one remaining massless. In this case the fractional spin is computed in terms of the dynamical degrees of freedom and shown to depend purely on the charge of the surviving abelian symmetry. Although this reduced model is shown to have its own solitonic configuration, it turns out to be trivial.
hep-th↗
On effects of gauging on symplectic structure, the Hopf term coupled to CP^1 model, and fractional spin
We couple the Hopf term to the relativistic $CP^1$ model and carry out the Hamiltonian analysis at the classical level. The symplectic structure of the model given by the set of Dirac Brackets among the phase space variables is found to be the same as that of the pure $CP^1$ model. This symplectic structure is shown to be inherited from the global SU(2) invariant $S^3$ model, and undergoes no modification upon gauging the U(1) subgroup, except the appearance of an additional first class constraint generating U(1) gauge transformation. We then address the question of fractional spin as imparted by the Hopf term at the classical level. For that we construct the expression of angular momentum through both symmetric energy-momentum tensor as well as through Noether's prescription. Both the expressions agree for the model indicating no fractional spin is imparted by this term at the classical level-a result which is at variance with what has been claimed in the literature. We provide an argument to explain the discrepancy and corroborate our argument by considering a radiation gauge fixed Hopf term coupled to $CP^1$ model, where the desired fractional spin is reproduced and is given in terms of the soliton number. Finally, by making the gauge field of the $CP^1$ model dynamical by adding the Chern-Simons term, the model ceases to be a $CP^1$ model, as is the case with its nonrelativistic counterpart. This model is also shown to reveals the existence of `anomalous' spin. This is however given in terms of the total charge of the system, rather than any soliton number.
hep-th↗
Constraints on Higher Dimensional Models for viable Extended Inflation
We consider two kinds of higher dimensional models which upon dimensional reduction lead to Jordan-Brans-Dicke type effective actions in four dimensions with the scale factor of the extra dimensions playing the role of the JBD field. These models are characterized by the potential for the JBD field which arises from the process of dimensional reduction, and by the coupling of the inflaton sector with the JBD field in the Jordan frame. Taking into account the fact that these models allow the possibility of enough inflation and dynamical compactification of the extra dimensions, we examine in the context of these models the other conditions which need to be satisfied for a viable scenario of extended inflation. We find that the requirements of conforming to general relativity at the present epoch, and producing suitable bubble spectrums during inflation lead to constraints on the allowed values taken by the parameters of these models. A model with a ten dimensional JBD field is able to satisfy the condition for appropriate density perturbations viewed in the conformal Einstein frame, with a stringent restriction on the initial value taken by the scale factor of the extra dimensions.
gr-qc↗