Browsing by Author "Balachandran, AP"

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    ANALYTICITY OF CHARGE-MONOPOLE SCATTERING-AMPLITUDE
    (American Physical Society, 1978-02-15) Balachandran, AP; Borchardt, S; Chang, SS; Stern, A; Cahalan, R; Ramachandran, R; Rupertsberger, H; Indian Institute of Science (IISC) - Bangalore; Western Kentucky University; Indian Institute of Technology System (IIT System); Indian Institute of Technology (IIT) - Kanpur; University of Vienna; University of Alabama Tuscaloosa
    We study the analyticity in cost of the exact quantum-mechanical electric-charge-magnetic-monopole scattering amplitude by ascribing meaning to its formally divergent partial-wave expansion as the boundary value of an analytic function. This permits us to find an integral representation for the amplitude which displays its analytic structure. On the physical sheet we find only a branch-point singularity in the forward direction, while on each of the infinitely many unphysical sheets we find a logarithmic branch-point singularity in the backward direction as well as the same forward structure. © 1978 The American Physical Society.
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    CORRECTION
    (American Physical Society, 1983) Balachandran, AP; University of Texas System; University of Texas Austin; University of Alabama Tuscaloosa
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    CORRECTION
    (American Physical Society, 1978-06-15) Balachandran, AP; Indian Institute of Science (IISC) - Bangalore; Western Kentucky University; Indian Institute of Technology System (IIT System); Indian Institute of Technology (IIT) - Kanpur; University of Vienna; University of Alabama Tuscaloosa
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    DOUBLY STRANGE DIBARYON IN THE CHIRAL MODEL
    (American Physical Society, 1984-03-12) Balachandran, AP; Barducci, A; Lizzi, F; Rodgers, VGJ; Stern, A; University of Texas System; University of Texas Austin; University of Alabama Tuscaloosa
    It shown that the chiral model with SU (3) flavor symmetry predicts a dibaryon state of low mass M (M2.2 GeV). It is electrically neutral and is an SU (3) singlet with JP=0+. It corresponds to a six-quark state found in the MIT bag model by Jaffe. It is also shown that there is no stable particlelike state of baryon number 2 which is based on Skyrme's spherically symmetric Ansatz for the chiral field. © 1984 The American Physical Society.
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    EXOTIC LEVELS FROM TOPOLOGY IN THE QUANTUM-CHROMODYNAMIC EFFECTIVE LAGRANGIAN
    (American Physical Society, 1982-10-18) Balachandran, AP; Nair, VP; Rajeev, SG; Stern, A; University of Texas System; University of Texas Austin; University of Alabama Tuscaloosa
    Skyrme has shown that the SU SU(2) chiral model has nontrivial topological sectors with static solutions for suitable Lagrangians. The baryon number B and strangeness of these sectors have been studied, and the existence of bound states of the nucleon field to the lightest solitons is shown. It is found that there must be long-lived levels with |B|6 and |s|6 and 1.8 GeV 5.6 GeV, some having half-integral charge and exotic relation between B and s, that can be pair produced in, say, e+e- collisions. © 1982 The American Physical Society.
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    GAUGE-THEORY OF EXTENDED OBJECTS
    (American Physical Society, 1979-07-15) Balachandran, AP; Stern, A; Skagerstam, BS; European Organization for Nuclear Research (CERN); University of Texas System; University of Texas Austin; University of Alabama Tuscaloosa
    Equations of motion and the Lagrangian formalism for extended objects coupled to Abelian and non-Abelian gauge fields are developed. These equations are minimal generalizations of the corresponding equations for point particles. It is seen that the string superconducts when it couples to an Abelian gauge field. Further, in this case, (a) the total charge on it is quantized, and (b) the total magnetic flux through it is quantized and conserved if it is closed and no segment of it is electrically neutral. The Lagrangians which lead to the equations of motion are not unique. Here, for a suitable Lagrangian, property (a) emerges at the classical level, the total charge being a topological invariant which labels the elements of 1[U(1)]. Both of these properties partially generalize to other extended objects and non-Abelian gauge fields. It is pointed out that for some Lagrangians, extended objects may have topological invariants (the analogs of total charge) for any gauge group. Supersymmetric extensions of the interaction Lagrangians are also outlined. For a point particle, such an extension correctly describes a spin-half particle in an Abelian or a non-Abelian gauge field. © 1979 The American Physical Society.
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    LAGRANGIAN AND HAMILTONIAN DESCRIPTIONS OF YANG-MILLS PARTICLES
    (American Physical Society, 1978-06-15) Balachandran, AP; Borchardt, S; Stern, A; Indian Institute of Science (IISC) - Bangalore; Western Kentucky University; Indian Institute of Technology System (IIT System); Indian Institute of Technology (IIT) - Kanpur; University of Vienna; University of Alabama Tuscaloosa
    A new Lagrangian L is proposed for the description of a particle with a non-Abelian charge in interaction with a Yang-Mills field. The canonical quantization of L is discussed. At the quantum level L leads to both irreducible and reducible multiplets of the particle depending upon which of the parameters in L are regarded as dynamical. The case which leads to the irreducible multiplet is the minimal non-Abelian generalization of the usual Lagrangian for a charged point particle in an electromagnetic field. Some of the Lagrangians proposed before for such systems are either special cases of ours or can be obtained from ours by simple modifications. Our formulation bears some resemblance to Dirac's theory of magnetic monopoles in the following respects: (1) Quantization is possible only if the values of certain parameters in L are restricted to a certain discrete set, this is analogous to the Dirac quantization condition; (2) in certain cases, L depends on external (nondynamical) directions in the internal-symmetry space. This is analogous to the dependence of the magnetic-monopole Lagrangian on the direction of the Dirac string. © 1978 The American Physical Society.
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    NON-LINEAR MODELS AS GAUGE-THEORIES
    (American Physical Society, 1979-04-15) Balachandran, AP; Stern, A; Trahern, G; European Organization for Nuclear Research (CERN); University of Texas System; University of Texas Austin; University of Alabama Tuscaloosa
    In the usual formulation of nonlinear models (such as chiral models), there is invariance under a nonlinear realization of a group GF which becomes linear when restricted to a subgroup HF. We formulate them so that they become gauge theories for a local group HC. It is the local version of a global group HC. When the gauge transformations are unrestricted at spatial infinity, only HC singlets are observable, and the usual formulation is recovered. When the gauge transformations are required to reduce to identity at spatial infinity, the usual formulation is no longer recovered. In particular, (1) nonsinglets under HC become observable, (2) the classical vacuum becomes degenerate under suitable conditions as in Yang-Mills theories, (3) the spontaneous symmetry breakdown of GF seems complete. (In the usual formulations, GF is broken down only to HF.) It is shown that the instanton and meron solutions of Yang-Mills theories are also solutions of certain nonlinear models. It is also shown that in a certain class of nonlinear models in (Euclidean) (3 + 1)-dimensional space-time, there are no instanton solutions for any choice of the groups. © 1979 The American Physical Society.
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    NONLOCAL CONSERVATION-LAWS FOR STRINGS
    (American Physical Society, 1982-09-15) Balachandran, AP; Stern, A; University of Texas System; University of Texas Austin; University of Alabama Tuscaloosa
    A finite number of nonlocal conservation laws are found in the Nambu-Goto string model. An infinite number of conserved currents may be obtained by embedding the string in more than 3 + 1 space-time dimensions. These currents resemble the nonlocal currents found in two-dimensional chiral models. © 1982 The American Physical Society.
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    ROTATIONALLY INVARIANT APPROXIMATION TO CHARGE-MONOPOLE SCATTERING
    (American Physical Society, 1978-02-15) Balachandran, AP; Borchardt, S; Chang, SS; Stern, A; Cahalan, R; Ramachandran, R; Rupertsberger, H; Western Kentucky University; Indian Institute of Technology System (IIT System); Indian Institute of Technology (IIT) - Kanpur; University of Vienna; University of Alabama Tuscaloosa
    A semiclassical approximation derived directly from the Feynman path integral is employed in the study of electric-charge-magnetic-monopole scattering. We show that this approximation, unlike perturbation theory, is consistent with rotational invariance. The semiclassical cross section is explicitly evaluated. It differs from the classical differential cross section for sufficiently large scattering angles due to the interference between the several classical trajectories contributing to the scattering at such angles. It is found that when the scattering angle is not too near the backward direction the semiclassical cross section approaches the classical limit rather slowly as the Dirac quantization number becomes large, or equally as 0 with the product of electric and magnetic charges held fixed. © 1978 The American Physical Society.