K.V Vasavada

• Ph.D
• Professor Emeritus at Indiana University – Purdue University Indianapolis

This paper discusses the philosophical concepts of Reality, Śūnya, and Śūnyatā which are integral parts of many Hindu and Buddhist scriptures from the perspective of a physicist. Amazingly, these concepts find strong parallels in areas of modern physics such as quantum physics and cosmology. These concepts in modern physics will be explained, and i...

Generalized superconvergence relations for KN and scattering are used to deduce parameters of the rho meson trajectory. Results are found to be in reasonable agreement with those from previous analyses using different methods.

We sum explicitly the left-hand side of the finite energy sum rules for the Veneziano amplitude. This shows that, for sufficiently large cutoff, the finite energy sum rules are satisfied with the leading contribution only. The actual sum contains other non-leading contributions.

We discuss the consequences of spectrally filtered optical feedback on the nonlinear dynamical response of a semiconductor laser. The spectral filter introduces two parameters, viz. the central frequency of the filter relative to the solitary laser frequency, and its bandwidth, which allow a control over the dynamical behavior of the laser. In part...

The dynamical intensity response of a semiconductor laser under the influence of injection current modulation, and the resulting hysteresis behavior, is investigated experimentally and theoretically. We report the first experimental observation, in a semiconductor laser, of the transition from a negative to a positive hysteresis as the modulation f...

We report the results of an experiment in which the cavity losses of a single mode, titanium sapphire laser are slowly varied with time. Under the influence of this slow sweep, the net gain required for the laser intensity to reach its lasing threshold increases beyond the static gain value necessary for lasing, a phenomenon called delayed bifurcat...

Through an investigation of the dynamics of solitons in three-level atoms, we demonstrate the possibility of optical pulse control and shaping in coherently driven media. It is also shown that solitons generated in three-level atoms, in contrast to two-level atoms, can propagate at the speed of light.

The propagation of a pair of electromagnetic pulses through a coherently prepared atomic medium in the Lambda configuration is studied. We find that even in an absorbing medium, it is possible to produce pulses that propagate shape invariant. The results reveal the spatiotemporal dynamics associated with field propagation, and highlight the role of...

The results of a numerical experiment are reported, in which the spatio-temporal propagation dynamics of a strong, primary and a weak, secondary pulse, in a coherently prepared atomic medium are investigated. Our ``measurements'' reveal the possibility of utilizing a coherently prepared medium to control the amplitude and phase of a pulse. The resu...

The results of a numerical experiment are reported, in which the spatio-temporal propagation dynamics of a strong, primary and a weak, secondary pulse, in a coherently prepared atomic medium are investigated. Our "measurements" reveal the possibility of utilizing a coherently prepared medium to control the amplitude and phase of a pulse. The result...

This paper reports results of a study on pulse-pair propagation through a coherently prepared medium (Phaseonium). The model consists of a A system, where the excited state |1〉 can decay at the rate 2γ out of the system. Through numerical simulations of the coupled Schroedinger-Maxwell equations, this paper addresses the question of how universal i...

This paper analyses the extraction of spectroscopic information on an atom via use of field fluctuations in a diode laser, wherein the statistics of diode-laser radiation are modeled by a phase-diffusion process. Using Monte Carlo methods, we solve density-matrix equations for a three-level V system, driven by this fluctuating field, tuned approxim...

We analyze the inversionless gain in a three-level ladder system by replacing the usual coherent coupling field with an incoherent field. Surprisingly, it is found that one can obtain inversionless amplification of a weak probe even in the absence of a coherent field in the model. We conclude that gain is determined by the ensemble average of the p...

We demonstrate the possibility of quenching the effects of noisy lasers by intense coherent fields. For this purpose, we study the spectrum of resonance fluorescence from two-level atoms irradiated by bichromatic fields, where one field is coherent and the other stochastic. The spectrum is seen to be very sensitive to the frequencies of the two fie...

Calculated nuclear relaxation rates in paramagnetic systems with are compared for the cases of fast and slow molecular tumbling. It is shown that the two treatments provide the same values before and after the low-field ωSτC = 1 dispersion, but differ in the dispersion region. Then the case of is considered in order to check whether it could be tre...

It is shown that the equivalence of the Lanczos and the conjugate gradient algorithms can be used to give a very powerful method to study linear systems in which complex symmetric matrices arise. This method is illustrated for electron spin resonance calculations, but is applicable to a wide class of problems in physics and engineering.

Analytical expressions are derived for spin-lattice and spin-spin relaxation times (T1M and T2M) of a nucleus arising from magnetic interactions (dipolar and contact) with a paramagnetic ion which has an anisotropic g tensor. The relaxation rates depend on the orientation of the ion-nucleus vector in the principal-axis system of the g tensor. The d...

The complex symmetric Lanczos algorithm (LA) has proven to be a very efficient means of calculating magnetic resonance line shapes and spectral densities associated with Fokker–Planck forms. However, the relative importance of the various components of the basis set in an accurate representation of the spectrum and the proper number of recursive st...

Using our previously described finite difference method an “exact” calculation for the linewidth of an exchanged collapsed doublet is presented under the conditions where the exchange time approaches the correlation time, conditions for which the standard theory of chemical exchange is not applicable. The model we use is that of two spins on separa...

The transverse relaxation expressions for two spins coupled via dipole-dipole interaction are obtained. It is shown how the expressions allow for the continuous transition from half widths of two spins (I and S) with different chemical shifts to the half width for identical spins (equal chemical shifts) where con be construed to be a cross-relaxati...

The 31P NMR chemical shift of beta-P of adenosine triphosphate (ATP) undergoes a substantial change (approximately 2-3 ppm) upon chelation of divalent ions such as Mg2+ or Ca2+. In the presence of nonsaturating amounts of Mg2+ or Ca2+, the lineshape of this resonance depends on the characteristic association and dissociation rates of these metal-AT...

31P NMR spectra of equilibrium mixtures of enzyme-bound reactants and products of the adenylate kinase reaction (formula; see text) were analyzed by using computer simulations based on density matrix theory of chemical exchange. Since adenylate kinase has the unique feature that the reactants in the reverse direction are both ADP molecules, which a...

A procedure is given for calculating the NMR lineshape of a cluster of spins imbedded in a molecule which is rotating with free or restricted motion. It is shown that for the isotropic diffusion model (assuming a correlation time τc such that 1/τc ⪢ HDD/lstrok;h where HDD is the dipole interaction) the line shape is Lorentzian as expected and has a...

It is demonstrated that the criterion for the determination of whether a spin-spin interaction (Jij) is “strong” or “weak” by comparing Jij with the corresponding chemical shift difference |ωi−ωj| needs modification in the presence of exchange, especially if rapid exchange conditions prevail. In particular, it is shown using computer-generated spec...

The density matrix theory of chemical exchange for the ABC ⇆ A′B′ + C′ system is presented. This theory provides a computational basis for the calculation of 31P NMR spectra of equilibrium mixtures of enzyme-bound reactants and products of phosphoryl transfer enzymes. The theory places no restrictions on the exchange rates or strength of spin-spin...

Meson bound state (higher twist) contribution to the ratio R(sigmaL/sigmaT) for deep inelastic leptoproduction is calculated in a model independent way. Significant contribution at low values of Q2 and x is found.

The constituent-interchange model is applied to inclusive vector-meson production in proton-proton collisions. In particular, production of psi, psi', and rho mesons is considered and good agreement with all the distributions is obtained.

DOI:https://doi.org/10.1103/PhysRevD.17.2515.2

A general model for the production of massive lepton pairs is discussed with emphasis on the predicted distributions of mass, transverse momentum, and longitudinal momentum. A comparison with proton-proton experiments is given and the fit is satisfactory for all three distributions. The model is essentially the constituent-interchange-model approac...

We point out that accurate measurements of the angular distributions of direct muons produced in hadronic collisions will have important consequences for various theoretical models for such processes. A number of models based on concepts of quark-partons and gluons are discussed within the context of the preliminary data available at present.

We saturate the matrix elements of the stress tensor between vector-meson states with f, f′, and the Pomeron, assuming that the coupling constants go like 1/mV2 (mV=vector-meson mass) within the symmetry-group (SU3, SU4, etc.) multiplet apart from the Clebsch-Gordan coefficients. It is found that (i) nonet (mass)2 formulas are obtained, (ii) vector...

We show that the zeros in the density matrix elements rhot1,-1 and Rerhos10 for K-p-->K¯*0n (K+n-->K*0p) are correlated and imply fundamental relationships among the Ball amplitudes following from partial conservation of strangeness-changing vector currents and the smoothness hypothesis.

We show that tensor dominance of the stress tensor and a scalar-tensor universality postulate lead to values of the DF ratio and the coupling constants of the f meson and Pomeron to nucleons in very good agreement with experiments.

We present experimental evidence that in pi-p-->rho0n, trho111-1~0 in an extended range of s and t and Re srho1110=0 at t~-mu2 independently of s. These two facts are shown to be correlated and imply fundamental relations between the Ball invariant amplitudes.

We include the Pomeron contribution in the tensor-meson dominance relations and find that (i) the previous discrepancies are resolved, (ii) the mass radii satisfy the Gell-Mann-Okubo type relations, and (iii) some bounds on the Pomeron slope and the tensor FD ratio, consistent with experiments, are obtained.

We have obtained a fit to most of the available data on pion-nucleon charge-exchange scattering using a model with Regge-Regge cuts. This shows quantitatively the importance of the double-Regge cuts, as opposed to the Regge-Pomeron cuts. We make comments on a recent work by Worden claiming that, in certain idealized limits, the Regge-Regge cuts in...

Recently it has been claimed that the coherent phase hypothesis of the P-wave amplitudes in ϱ° production is wrong. We show that this conclusion is not valid.

In studying the single-pion production amplitudes in the vector-meson mass range (ρ and K*) we observed zeros and structures in Reρ1011 and ρ1-111 density matrix elements. The zero of Reρ1011 is observed to be approximately independent of beam momentum, charge state, or strangeness of the vector meson and is invariant under s-t crossing at Δ2≈mv2-m...

Recently it has been claimed that the coherent phase hypothesis of the P wave amplitudes in rhoo production is wrong. We show that this conclusion is not valid.

Normalizable wave functions are constructed for bound states and resonances from the S-matrix quantities. The bound-state wave function is of the Schrödinger type. The Schrödinger equation does not give normalizable wave functions for resonances. Thus the resonance wave function is of the non-Schrödinger type. An S-matrix model is constructed to ge...

We have measured the production and decay angular distributions of the reaction π+p→πOΔ++ at 13.1 GeV/c incident momentum. For −t > 0.1 (GeV/c)2 the data is well described by M1 ϱ-exchange models, the best results being obtained from a weak cut model with a wrong signature nonsense zero. For −t < 0.1 (GeV/c)2 there is evidence for the existence of...

We have measured the production and decay angular distributions of the reaction pi+p-->piODelta++ at 13.1 GeV/c incident momentum. For -t > 0.1 (GeV/c)2 the data is well described by M1 varrho-exchange models, the best results being obtained from a weak cut model with a wrong signature nonsense zero. For -t < 0.1 (GeV/c)2 there is evidence for the...

It is suggested that the high-energy unitarity condition and Regge cuts can be built into the Veneziano model by dispersing the representation in trajectory parameters. In particular, a model of the Amati-Fubini-Stanghellini type and the optical model are considered in order to obtain the spectral functions of the integral representations.

Some interesting properties of the Regge cuts obtained by multiple exchange of non-Pomeranchuk type Regge poles are discussed and their possible role in explanation of recurring minima and polarizations of high energy reactions is pointed out.

Continuous-moment sum rules with different weight functions are studied for the single-pion photo-production process. Even granting the usual ambiguities on the high-energy side, it seems that presently available very low-energy data may be in considerable error.

We show that the Veneziano-Lovelace one-term formula for pion-pion scattering, although a good first approximation, has some undesirable features. With the help of a few secondary terms, a model amplitude, which is consistent with the known properties of the pion-pion system up to the f0 mass region and the high-energy phenomenology, is constructed...

Electron scattering from diatomic molecular systems including coupling of partial waves in fixed-nuclei approximation

A previous analysis of electron scattering from diatomic molecular systems in spherical coordinates is generalized to include the coupling of different partial waves in the fixed-nuclei approximation. The factorability between dynamical parameters and those depending on inter-nuclear-axis orientation can be maintained, and the optical theorem is sh...

A method, discussed in a previous paper, of evaluating the high-energy contributions to current-algebra sum rules is applied to several well-known sum rules. These include (i) the Adler-Weisberger sum rule for the pi-pi system, using pi-pi phase shifts, (ii) the Cabibbo-Radicati sum rule, (iii) pi-N sum rules, and (iv) the pi-N spin-flip sum rule....

A method to evaluate high-energy contributions to current-algebra sum rules by combining them with finite-energy sum rules is suggested. Applications are made to the Adler-Weisberger-type sum rules for the $$\pi${}$-${}$\pi${}$ and the $K$-${}$\pi${}$ systems, and to various sum rules for the pion photoproduction process. It is shown that the forme...

Vector-meson-nucleon form factors obtained from high-energy, large-momentum-transfer pp scattering are used to determine the proton magnetic form factor GMpmup. With essentially one adjustable parameter, all present large-momentum-transfer data can be fitted. The neutron magnetic form factor GMnmun is predicted and is found to have a zero at Delta2...

DOI:https://doi.org/10.1103/PhysRev.176.2168.4

Continuous-moment sum rules are used for examining the validity of the pion-conspiracy hypothesis in pion photoproduction. The trajectory and residue functions of the pion and conspirator trajectories are estimated.

Generalized dispersion sum rules are used for determining the A2 trajectory and residue function in pion photoproduction. Our results favor the Gell-Mann mechanism of ghost elimination for the A2 over the Chew and no-compensation mechanisms.

The problem of maintaining the locality of the bound-state wave function is discussed in the S-matrix approach to the first-order energy shift. It is shown first that the nearby-singularity prescription in the Dashen-Frautschi formalism leads to the inclusion of unphysical terms coming from the nonlocal component of the wave function. It is pointed...

Results of calculations for bound and scattering states in off-mass-shell and on-mass-shell formalisms are compared by considering the solutions of the Bethe-Salpeter equation in the ladder approximation, and those of the exact $\frac{N}{D}$ equations. The case of two scalar equal-mass particles interacting via the exchange of a third scalar partic...

The problem of obtaining the generalized potential in the physical region for a given partial wave from the experimentally known phase shifts for that channel is examined. We consider the piN system, where the phase shifts are now well known up to reasonably high energies in various partial waves, and compute the generalized potentials for the P33,...

A bootstrap of the K* meson is attempted in the Kpi channel via a representation due to Abbe, Kaus, Nath, and Srivastava. Here a total amplitude is constructed purely in terms of Regge trajectories, and crossing is used to determine the parameters. An unknown coupling constant GrhoKK¯ enters the calculation. When we take its SU(3) value, our bootst...

A generalization of the method of polarized orbitals is introduced to calculate the scattering of electrons from diatomic molecules in the Born-Oppenheimer (fixed-nuclei) approximation. The molecule is described by a single-center expansion which in lowest order is spherically symmetric and therefore an atomic-like function. This function can be po...

The P11 partial wave of the piN system is characterized by a large absorption and a resonance (possibly inelastic) at 575-MeV laboratory pion energy (Roper resonance). In view of these features of the P11 channel, the piN system may be rendered sufficiently weak not to bind the nucleon. Using the experimental mass of the nucleon and the recently ob...

We estimate the nucleon radius from the pion-nucleon phase shifts, assuming that the nucleon is a bound state of the pion and the nucleon. The calculation is based on the one-pole approximation of the Gelfand-Levitan formalism on the inverse scattering problem. The numerical result of 0.15-0.50 F is obtained for the radius. In this connection, we d...

We have studied the dynamics of the I=1, J=32+ K¯Ξ and KN systems by the Balázs-type ND method and have observed a typical feature of this procedure for treating the far left-hand singularities. The dynamical singularities of the partial-wave amplitude are assumed to arise mainly from the nearby cut (due to Σ and Λ exchange in the crossed channel)...

Recently discovered spin-2 mesons f, A2, f'(1500), and K**(1405) are considered as resonances in various systems containing two pseudoscalar mesons with appropriate quantum numbers. Making the single-channel approximation, exact ND calculations are done by solving the integral equations with the help of the matrix inversion method. The input forces...

A dynamical calculation using Balázs typesN/D method is performed for theT=2 Σ-π system inP 3/2 state. Self-consistent solutions for the position and residue of a resonance are obtained for a wide range of the relevant Yukawa coupling constants and different sets of matching points. Some remarks are made regarding interpretation of the results

A dispersion theoretic approach is made within the framework of partial wave dispersion relations to understand the pionic disintegration of the deuteron at low energies. The reaction amplitude is expressed in terms of six independent Lorentz invariant scalar functions which are free from kinematical singularities, and the partial wave helicity amp...