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Articles 1  30 of 517
FullText Articles in Physics
New Exactly Solvable Hamiltonians  Shape Invariance And SelfSimilarity, David Barclay, Ranabir Dutt, Asim Gangopadhyaya, Avinash Khare, A. Pagnamenta, Uday Sukhatne
New Exactly Solvable Hamiltonians  Shape Invariance And SelfSimilarity, David Barclay, Ranabir Dutt, Asim Gangopadhyaya, Avinash Khare, A. Pagnamenta, Uday Sukhatne
Asim Gangopadhyaya
We discuss in some detail the selfsimilar potentials of Shabat and Spiridonov which are reflectionless and have an infinite number of bound states. We demonstrate that these selfsimilar potentials are in fact shape invariant potentials within the formalism of supersymmetric quantum mechanics. In particular, using a scaling ansatz for the change of parameters, we obtain a large class of new, reflectionless, shape invariant potentials of which the ShabatSpiridonov ones are a special case. These new potentials can be viewed as qdeformations of the single soliton solution corresponding to the RosenMorse potential. Explicit expressions for the energy eigenvalues, eigenfunctions and transmission ...
Generation Of A Complete Set Of Additive ShapeInvariant Potentials From An Euler Equation, Jonathan Bougie, Asim Gangopadhyaya, Jeffrey Mallow
Generation Of A Complete Set Of Additive ShapeInvariant Potentials From An Euler Equation, Jonathan Bougie, Asim Gangopadhyaya, Jeffrey Mallow
Asim Gangopadhyaya
In supersymmetric quantum mechanics, shape invariance is a sufficient condition for solvability. We show that all conventional additive shapeinvariant superpotentials that are independent of ħ can be generated from two partial differential equations. One of these is equivalent to the onedimensional Euler equation expressing momentum conservation for inviscid fluid flow, and it is closed by the other. We solve these equations, generate the set of all conventional shapeinvariant superpotentials, and show that there are no others in this category. We then develop an algorithm for generating all additive shapeinvariant superpotentials including those that depend on ħ explicitly.
Supersymmetry And The Tunneling Problem In An Asymmetric Double Well, Asim Gangopadhyaya, Prasanta Panigrahi, Uday Sukhatne
Supersymmetry And The Tunneling Problem In An Asymmetric Double Well, Asim Gangopadhyaya, Prasanta Panigrahi, Uday Sukhatne
Asim Gangopadhyaya
The techniques of supersymmetric quantum mechanics are applied to the calculation of the energy difference between the ground state and the first excited state of an asymmetric double well. This splitting, originating from the tunneling effect, is computed via a systematic, rapidly converging perturbation expansion. Perturbative calculations to any order can be easily carried out using a logarithmic perturbation theory. Our approach yield substantially better results than alternative widely used semiclassical analyses.
Magnet Traveling Through A Conducting Pipe: A Variation On The Analytical Approach, Benjamin Irvine, Matthew Kemnetz, Asim Gangopadhyaya, Thomas Ruubel
Magnet Traveling Through A Conducting Pipe: A Variation On The Analytical Approach, Benjamin Irvine, Matthew Kemnetz, Asim Gangopadhyaya, Thomas Ruubel
Asim Gangopadhyaya
We present an analytical study of magnetic damping. In particular, we investigate the dynamics of a cylindrical neodymium magnet as it moves through a conducting tube. Owing to the very high degree of uniformity of the magnetization for neodymium magnets, we are able to provide completely analytical results for the electromotive force generated in the pipe and the consequent retarding force. Our analytical expressions are shown to have excellent agreement with experimental observations.
Noncentral Potentials And Spherical Harmonics Using Supersymmetry And Shape Invariance, Ranabir Dutt, Asim Gangopadhyaya, Uday Sukhatne
Noncentral Potentials And Spherical Harmonics Using Supersymmetry And Shape Invariance, Ranabir Dutt, Asim Gangopadhyaya, Uday Sukhatne
Asim Gangopadhyaya
It is shown that the operator methods of supersymmetric quantum mechanics and the concept of shape invariance can profitably be used to derive properties of spherical harmonics in a simple way. The same operator techniques can also be applied to several problems with noncentral vector and scalar potentials. As examples, we analyze the bound state spectra of an electron in a Coulomb plus an Aharonov – Bohm field and/or in the magnetic field of a Dirac monopole.
Supersymmetric Quantum Mechanics And Solvable Models, Asim Gangopadhyaya, Jonathan Bougie, Jeffrey Mallow, C. Rasinariu
Supersymmetric Quantum Mechanics And Solvable Models, Asim Gangopadhyaya, Jonathan Bougie, Jeffrey Mallow, C. Rasinariu
Asim Gangopadhyaya
We review solvable models within the framework of supersymmetric quantum mechanics (SUSYQM). In SUSYQM, the shape invariance condition insures solvability of quantum mechanical problems. We review shape invariance and its connection to a consequent potential algebra. The additive shape invariance condition is specified by a differencedifferential equation; we show that this equation is equivalent to an infinite set of partial differential equations. Solving these equations, we show that the known list of hindependent superpotentials is complete. We then describe how these equations could be extended to include superpotentials that do depend on h.
Comment On "Ideal Capacitor Circuits And Energy Conservation" By K. Mita And M. Boufaida [Am. J. Phys. 67 (8), 737739 (1999)], Asim Gangopadhyaya, Jeffrey Mallow
Comment On "Ideal Capacitor Circuits And Energy Conservation" By K. Mita And M. Boufaida [Am. J. Phys. 67 (8), 737739 (1999)], Asim Gangopadhyaya, Jeffrey Mallow
Asim Gangopadhyaya
No abstract provided.
Semiclassical Approach To QuantumMechanical Problems With Broken Supersymmetry, Ranabir Dutt, Asim Gangopadhyaya, Avinash Khare, A. Pagnamenta, Uday Sukhatne
Semiclassical Approach To QuantumMechanical Problems With Broken Supersymmetry, Ranabir Dutt, Asim Gangopadhyaya, Avinash Khare, A. Pagnamenta, Uday Sukhatne
Asim Gangopadhyaya
The semiclassical WKB approximation method is reexamined in the context of nonrelativistic quantummechanical boundstate problems with broken supersymmetry (SUSY). This gives rise to an alternative quantization condition (denoted by BSWKB) which is different from the standard WKB formula and also different from the previously studied supersymmetric (SWKB) formula for unbroken SUSY. It is shown that to leading order in ħ, the BSWKB condition yields exact energy eigenvalues for shapeinvariant potentials with broken SUSY (harmonic oscillator, PöschlTeller I and II) which are known to be analytically solvable. Further, we show explicitly that the higherorder corrections to these energy eigenvalues, up to ...
Renormalization Group Equations In Broken Supersymmetric Theories Using Superspace Methods, Asim Gangopadhyaya, Darwin Chang
Renormalization Group Equations In Broken Supersymmetric Theories Using Superspace Methods, Asim Gangopadhyaya, Darwin Chang
Asim Gangopadhyaya
We apply the superfield method with the spurion technique to derive the renormalizationgroup equations in broken supersymmetric theories. We point out some possible ambiguities in this procedure and show that it is in general necessary to express the supersymmetrybreaking terms in explicit Dtype form. We also found that it is possible to construct broken supersymmetric theories where some of the symmetrybreaking parameters do not receive any infinite renormalization.
Comment On ‘‘The Hidden Symmetry For A Quantum System With An Infinitely Deep SquareWell Potential By ShiHai Dong And ZhongQi Ma [Am. J. Phys. 70 (5) 520521 (2002)], Asim Gangopadhyaya, Jeffrey Mallow
Comment On ‘‘The Hidden Symmetry For A Quantum System With An Infinitely Deep SquareWell Potential By ShiHai Dong And ZhongQi Ma [Am. J. Phys. 70 (5) 520521 (2002)], Asim Gangopadhyaya, Jeffrey Mallow
Asim Gangopadhyaya
No abstract provided.
Gravitational Slingshot , John Dykla, Robert Cacioppo, Asim Gangopadhyaya
Gravitational Slingshot , John Dykla, Robert Cacioppo, Asim Gangopadhyaya
Asim Gangopadhyaya
The slingshot effect is an intriguing phenomenon that has been used effectively by NASA to send spacecraft to outer edges of the solar system. This phenomenon can be satisfactorily explained by Newtonian physics. However, if it is presented as a problem involving fourmomentum conservation, the methods of relativistic kinematics easily lead to the conditions necessary for an accelerating as well as a retarding scenario. This problem provides an example that showcases the frequent utility of relativistic methods to analyze problems of Newtonian mechanics.
Magnetic Transitions In Disordered Gdal_{2}, D. Williams, Paul Shand, Thomas Pekarek, Ralph Skomski, Valeri Petkov, Diandra LesliePelecky
Magnetic Transitions In Disordered Gdal2, D. Williams, Paul Shand, Thomas Pekarek, Ralph Skomski, Valeri Petkov, Diandra LesliePelecky
Thomas M. Pekarek
The role of disorder in magnetic ordering transitions is investigated using mechanically milled GdAl2. Crystalline GdAl2 is a ferromagnet while amorphous GdAl2 is a spin glass. Nanostructured GdAl2 shows a paramagnetictoferromagnetic transition and glassy behavior, with the temperature and magnitude of each transition dependent on the degree and type of disorder. Disorder is parametrized by a Gaussian distribution of Curie temperatures TC with mean TC and breadth Δ TC. A nonzero coercivity is observed at temperatures more than 20 K above the highest TC of any known GdAl phase; however, the coercivity decreases with decreasing temperature over the same temperature ...
New Solvable Singular Potentials , R. Dutt, Asim Gangopadhyaya, C. Rasinariu, Uday Sukhatne
New Solvable Singular Potentials , R. Dutt, Asim Gangopadhyaya, C. Rasinariu, Uday Sukhatne
Asim Gangopadhyaya
We obtain three new solvable, real, shape invariant potentials starting from the harmonic oscillator, PöschlTeller I and PöschlTeller II potentials on the halfaxis and extending their domain to the full line, while taking special care to regularize the inverse square singularity at the origin. The regularization procedure gives rise to a deltafunction behavior at the origin. Our new systems possess underlying nonlinear potential algebras, which can also be used to determine their spectra analytically.
InterRelations Of Solvable Potentials, Asim Gangopadhyaya, Prasanta Panigrahi, Uday Sukhatne
InterRelations Of Solvable Potentials, Asim Gangopadhyaya, Prasanta Panigrahi, Uday Sukhatne
Asim Gangopadhyaya
Solvable Natanzon potentials in nonrelativistic quantum mechanics are known to group into two disjoint classes depending on whether the Schrödinger equation can be reduced to a hypergeometric or a confluent hypergeometric equation. All the potentials within each class are connected via point canonical transformations. We establish a connection between the two classes with appropriate limiting procedures and redefinition of parameters, thereby interrelating all known solvable potentials.
DisorderInduced Depression Of The Curie Temperature In Mechanically Milled Gdal_{2}, Marco Morales Torres, D. Williams, Paul Shand, C. Stark, Thomas Pekarek, L. Yue, Valeri Petkov, Diandra LesliePelecky
DisorderInduced Depression Of The Curie Temperature In Mechanically Milled Gdal2, Marco Morales Torres, D. Williams, Paul Shand, C. Stark, Thomas Pekarek, L. Yue, Valeri Petkov, Diandra LesliePelecky
Thomas M. Pekarek
The effect of disorder on the ferromagnetic transition is investigated in mechanically milled GdAl2. GdAl2is a ferromagnet when crystalline and a spin glass when amorphous. Mechanical milling progressively disorders the alloy, allowing observation of the change from ferromagnetic to a disordered magnetic state. Xray diffraction and pairdistributionfunction analysis are used to determine the grain size, lattice parameter, and meansquared atomic displacements. The magnetization as a function of temperature is described by a Gaussian distribution of Curie temperatures. The mean Curie temperature decreases with decreasing lattice parameter, where lattice parameter serves as a measure of defect concentration. Two different rates of ...
Unintended Consequences Of Imprecise Notation – An Example From Mechanics, Asim Gangopadhyaya, Gordon Ramsey
Unintended Consequences Of Imprecise Notation – An Example From Mechanics, Asim Gangopadhyaya, Gordon Ramsey
Asim Gangopadhyaya
We present a conundrum that results from the imprecise use of notation for partial derivatives. Taking an example from mechanics, we show that lack of proper care in re presenting partial derivatives in Lagrangian and Hamiltonian formulations paradoxically leads to two different values for the time derivative of the canonical momentum. This problem also exists in other areas of physics,such as thermodynamics.
Coordinate Realizations Of Deformed Lie Algebras With Three Generator, Ranabir Dutt, Asim Gangopadhyaya, C. Rasinariu, Uday Sukhatne
Coordinate Realizations Of Deformed Lie Algebras With Three Generator, Ranabir Dutt, Asim Gangopadhyaya, C. Rasinariu, Uday Sukhatne
Asim Gangopadhyaya
Differential realizations in coordinate space for deformed Lie algebras with three generators are obtained using bosonic creation and annihilation operators satisfying Heisenberg commutation relations. The unified treatment presented here contains as special cases all previously given coordinate realizations of so(2,1), so(3), and their deformations. Applications to physical problems involving eigenvalue determination in nonrelativistic quantum mechanics are discussed.
Translational Shape Invariance And The Inherent Potential Algebra, Asim Gangopadhyaya, Jeffrey Mallow, Uday Sukhatne
Translational Shape Invariance And The Inherent Potential Algebra, Asim Gangopadhyaya, Jeffrey Mallow, Uday Sukhatne
Asim Gangopadhyaya
For all quantummechanical potentials that are known to be exactly solvable, there are two different, and seemingly independent methods of solution. The first approach is the potential algebra of symmetry groups; the second is supersymmetric quantum mechanics, applied to shapeinvariant potentials, which comprise the set of known exactly solvable potentials. Using the underlying algebraic structures of Natanzon potentials, of which the translational shapeinvariant potentials are a special subset, we demonstrate the equivalence of the two methods of solution. In addition, we show that, while the algebra for the general Natanzon potential is so(2,2), the subgroup so(2,1 ...
Anyonic Superconductivity In A Modified LargeU Hubbard Model, Asim Gangopadhyaya, Prasanta Panigrahi
Anyonic Superconductivity In A Modified LargeU Hubbard Model, Asim Gangopadhyaya, Prasanta Panigrahi
Asim Gangopadhyaya
A modified largeU Hubbard model at half filling is analyzed by a meanfield approach. Preserving a local U(1) symmetry of the action, the fluctuations about half filling are studied in the spirit of the commensuratefluxphase condition. The fluctuations then contribute a ChernSimons term to the treelevel Lagrangian with a coefficient appropriate to that of a half fermion. With the Coulomb repulsion term, we study the lowenergy excitations of the model and show the existence of superconductivity in the presence of a fourFermi interaction term.
Superspace Ward Identities In Supersymmetric Gauge Theories, Asim Gangopadhyaya, Darwin Chang
Superspace Ward Identities In Supersymmetric Gauge Theories, Asim Gangopadhyaya, Darwin Chang
Asim Gangopadhyaya
In superspace formulation of supersymmetric gauge theories, gauge invariance requires an infinite set of identities between the infinite set of renormalization constants. Using Ward identities in superspace, the same is derived. These identities at one loop level are also demonstrated.
The Electric Field At The Chargeless Interface Between Two Regions Of Space, Asim Gangopadhyaya, Robert Mcnees
The Electric Field At The Chargeless Interface Between Two Regions Of Space, Asim Gangopadhyaya, Robert Mcnees
Asim Gangopadhyaya
A common method for solving Poisson's equation in electrostatics is to patch together two or more solutions of Laplace's equation using boundary conditions on the potential and its gradient. Other methods may generate solutions without the need to check these conditions explicitly, and reconciling these solutions with the appropriate boundary conditions can be surprisingly subtle. As a result, a student may arrive at paradoxical conclusions—even in the case of elementary problems—that seem to be at odds with basic physical intuition. We illustrate this issue by showing how the potential of a uniformly charged ring appears to ...
Heterotic Conformal Field Theory And Gepner’S Construction, Darwin Chang, Asim Gangopadhyaya, Alok Kumar, Jin Wang
Heterotic Conformal Field Theory And Gepner’S Construction, Darwin Chang, Asim Gangopadhyaya, Alok Kumar, Jin Wang
Asim Gangopadhyaya
We discuss some general properties of heterotic conformal field theory in which conformal anomalies c are different for the leftmoving and rightmoving sectors. It is precisely this type of theory that can be applied immediately to the construction of heterotic string theory. We discuss a general way of constructing such a theory using free fermions. The construction is then applied to generalize Gepner's construction of superstring solutions using the tensor products of N=2 superconformal field theories.
The Surface Stability Of Cos_{2}(100), Ning Wu, Renat F. Sabirianov, ChunGang Duan, WaiNing Mei, David Wisbey, Yaroslav B. Losovyj, M. Manno, C. Leighton, En Cai, Jiandi Zhang, Peter A. Dowben
The Surface Stability Of Cos2(100), Ning Wu, Renat F. Sabirianov, ChunGang Duan, WaiNing Mei, David Wisbey, Yaroslav B. Losovyj, M. Manno, C. Leighton, En Cai, Jiandi Zhang, Peter A. Dowben
Ning Wu
The stability of various possible terminations of the CoS2 (1 × 1) surface have been explored and theoretical expectations are found to agree with experiment. With extensive annealing, there is a phase separation at the (100) surface of CoS2. Sulfur segregation to the surface leads to a significant change in the largely sulfur bands due to changes in the hybridized bands, with cobalt. Resonant photoemission spectra indicate clearly that the hybridized cobalt and sulfur bands, characteristic of the CoS2 bulk, lie at higher binding energies than those of segregated sulfur layers. This is discussed in terms of the stability of various ...
Preferential Perpendicular Acceleration Of Heavy Ionospheric Ions By Interactions With Electrostatic Hydrogen Cyclotron Waves, Nagendra Singh, Robert W. Schunk, Jan Josef Sojka
Preferential Perpendicular Acceleration Of Heavy Ionospheric Ions By Interactions With Electrostatic Hydrogen Cyclotron Waves, Nagendra Singh, Robert W. Schunk, Jan Josef Sojka
Jan J. Sojka
The energization of heavy ionospheric ions by electrostatic hydrogen cyclotron (EHC) waves is examined. In particular, the problem of preferential perpendicular acceleration of heavy ions above 5000 km along auroral field lines is examined critically. Observations have indicated that above this altitude the occurrences of ion beams and EHC waves are highly correlated and that the occurrence rates are high. The EHC waves are found to be coherent. The energization process is examined in the light of interactions of a single coherent wave with the ions. The interactions can be stochastic or nonstochastic, depending on the parameters of the wave ...
FarField Scattering Of A NonGaussian OffAxis Axisymmetric Laser Beam By A Spherical Particle, James A. Lock, Joseph T. Hodges
FarField Scattering Of A NonGaussian OffAxis Axisymmetric Laser Beam By A Spherical Particle, James A. Lock, Joseph T. Hodges
James A. Lock
Experimental laser beam profiles often deviate somewhat from the ideal Gaussian shape of the axisymmetric TEM(00) laser mode. To take these deviations into account when calculating light scattering of an offaxis beam by a spherical particle, we use our phasemodeling method to approximate the beamshape coefficients in the partial wave expansion of an experimental laser beam. We then use these beamshape coefficients to compute the nearforward direction scattering of the offaxis beam by the particle. Our results are compared with laboratory data, and we give a physical interpretation of the various features observed in the angular scattering patterns. (C ...
LongLasting Phosphorescence In Basi_{2}O_{2}N_{2}:Eu^{2+} And Ba_{2}Sio_{4}:Eu^{2+} Phases For XRay And Cathode Ray Tubes, Meiyuan Wang, Xia Zhang, Zhendong Hao, Xinguang Ren, Yongshi Luo, Haifeng Zhao, XiaoJun Wang, Jiahua Zhang
LongLasting Phosphorescence In Basi2O2N2:Eu2+ And Ba2Sio4:Eu2+ Phases For XRay And Cathode Ray Tubes, Meiyuan Wang, Xia Zhang, Zhendong Hao, Xinguang Ren, Yongshi Luo, Haifeng Zhao, XiaoJun Wang, Jiahua Zhang
XiaoJun Wang
We report the longlasting bluishgreen phosphorescence for Xray or cathode ray tubes in the phosphors with compositions of either Ba2SiO4:0.01Eu2+–xSi3N4 (x=0–1) or 2BaCO3–ySi3N4:0.01Eu2+(y=1/6–1) synthesized by a solidstate reaction. By tuning the Si3N4content, the phosphorescence may originate from Eu2+ in BaSi2O2N2(peaking at 490 nm), Ba2SiO4 (505 nm), and Ba3SiO5 (590 nm) phases. The strong phosphorescence of the Ba2SiO4:Eu2+ phase in 2BaCO3–ySi3N4:0.01Eu2+ is attributed to N substitution for O to generate a shallow trap. In Ba2SiO4:0.01Eu2+–xSi3N4 , however, N prefers reacting with Ba2SiO4 ...
Effects Of Dissociative Recombination On The Composition Of Planetary Atmospheres, Jane L. Fox
Effects Of Dissociative Recombination On The Composition Of Planetary Atmospheres, Jane L. Fox
Jane L. Fox
Because dissociative recombination (DR) reactions of molecular ions are often highly exothermic, in the thermospheres of the Earth and planets DR may be a source of translationally and internally excited fragments. DR is important, therefore, for thermospheric neutral heating; if the excited fragments radiate to space, however, DR may be also a source of thermospheric cooling. DR may produce metastable fragments, which may live long enough to participate in reactions that are not available to ground state species. It is rare, however, for DR to be a significant source of minor species in their ground states. An exception appears to ...
Theoretical Study Of Anomalously High F Region Peak Altitudes In The Polar Ionosphere, Jan Josef Sojka, Robert W. Schunk
Theoretical Study Of Anomalously High F Region Peak Altitudes In The Polar Ionosphere, Jan Josef Sojka, Robert W. Schunk
Jan J. Sojka
During the last solar maximum period several observations of anomalously high F region peak altitudes have been made by the high latitude incoherent scatter radars. The observations indicate that there are several distinctive features associated with these high h_{m}F_{2} ionospheric profiles: (1) they are observed near midnight with the plasma flowing out of the polar cap, (2) N_{m}F_{2} ranges from 105 to 106 cm−3, (3) h_{m}F_{2} ranges from 400 to 500 km, (4) below 300 km the profile is devoid of ionization, and (5) the observations are for solar maximum ...
TwoLayer HallEffect Model With Arbitrary SurfaceDonor Profiles: Application To Zno, David C. Look
TwoLayer HallEffect Model With Arbitrary SurfaceDonor Profiles: Application To Zno, David C. Look
David C. Look
A complete twolayer Halleffect model, allowing arbitrary donor and acceptor profiles, is presented and applied to the problem of conductive surface layers in ZnO. Temperaturedependent mobility and carrier concentration data in the temperature range of 20–320 K are fitted with an efficient algorithm easily implemented in commercial mathematics programs such as MATHCAD. The model is applied to two ZnO samples, grown by the melt (MLT) and hydrothermal (HYD) processes, respectively. Under the assumption of a “square” surfacedonor profile, the fitted surfacelayer thicknesses are 48 and 2.5 nm, respectively, for the MLT and HYD samples. The surfacedonor concentrations are ...
Vanadium Oxide ThinFilm Variable ResistorBased Rf Switches, Kuanchang Pan, Weisong Wang, Eunsung Shin, Kelvin Freeman, Guru Subramanyam
Vanadium Oxide ThinFilm Variable ResistorBased Rf Switches, Kuanchang Pan, Weisong Wang, Eunsung Shin, Kelvin Freeman, Guru Subramanyam
Guru Subramanyam
Vanadium dioxide (VO2) is a unique phase change material (PCM) that possesses a metaltoinsulator transition property. Pristine VO2 has a negative temperature coefficient of resistance, and it undergoes an insulatortometal phase change at a transition temperature of 68°C. Such a property makes the VO2 thinfilmbased variable resistor (varistor) a good candidate in reconfigurable electronics to be integrated with different RF devices such as inductors, varactors, and antennas. Series singlepole singlethrow (SPST) switches with integrated VO2 thin films were designed, fabricated, and tested. The overall size of the device is 380 μm × 600 μm. The SPST switches were fabricated on ...