ASE suppression in Er3+ doped dual-core triangular lattice Photonic Crystal Fibers (PCFs) for communication wavelength

In this article, silica based triangular lattice PCF has been investigated towards both narrowband and broadband dispersion compensation for application in the communication wavelength. A dual core structure is obtained by introducing two different air-hole diameters in the cladding of the PCF. Dependence of individual structural parameters towards high negative dispersion (both narrowband and broadband) has been investigated in details with multipole mode based solver. The numerical investigation exhibits narrowband of very large negative dispersion of -37,300 ps/nm/km around the wavelength of 1550 nm. Present investigation also reports broadband dispersion values varying from -800 ps/nm/km to -2600 ps/nm/km over a 200 nm wavelength (1400 nm to 1600 nm) range, and kappa values near 300 nm, which matches well with standard single mode fiber. Using the principle of power transfer from the inner core to the outer core after the coupling wavelength, we have investigated possible design of ASE suppressed amplifier in which wavelengths after the coupling wavelength cannot be amplified as most of the power tunnel to the outer core, where doped ion does not exist.Comment: 8 pages, 13 figure

Designing an ultra negative dispersion Photonic Crystal Fiber (PCFs) with square lattice geometry

In this article we have theoretically investigated the dispersion characteristics of dual-core PCF, based on square-lattice geometry by varying different parameters. The fiber exhibits a very large negative dispersion because of rapid slope change of the refractive indices at the coupling wavelength between the inner core and outer core. The dependence of different geometrical parameters namely hole-to-hole spacing (pitch) and different air-hole diameter (d) was investigated in detail. By proper adjustment of the available parameters, a high negative dispersion value of -47,500 ps/nm/km has been achieved around the wavelength of 1550nm. Our proposed fiber will be an excellent device for dispersion compensation in long-haul data transmission as being thousand times more than the available DCFs.Comment: 6 pages, 12 graph

Nonquantum Cognition

The Hilbert space structure of classical field theory is proposed as a general theoretical framework to model human cognitive processes which do not often follow classical (Bayesian) probability principles. This leads to an extension of the circumplex model of affect and a Poincar\'{e} sphere representation. A specific toy field theoretic model of the brain as a coherent structure in the presence of noise is also proposed that agrees qualitatively with Pavlovian fear conditioning studies.Comment: 24 pages, 2 figure

String worldsheet theory in hamiltonian framework and background independence

We analyze exact conformal invariance of string worldsheet theory in non-trivial backgrounds using hamiltonian framework. In the first part of this talk we consider the example of type IIB superstrings in Ramond-Ramond pp-wave background. In particular, we discuss the quantum definition of energy-momentum (EM) tensor and two methods of computing Virasoro algebra. One of the methods uses dynamical supersymmetries and indirectly establishes (partially) conformal invariance when the background is on-shell. We discuss the problem of operator ordering involved in the other method which attempts to compute the algebra directly. This method is supposed to work for off-shell backgrounds and therefore is more useful. In order to understand this method better we attempt a background independent formulation of the problem which is discussed in the second half of the talk. For a bosonic string moving in an arbitrary metric-background such a framework is obtained by following DeWitt's work (Phys.Rev.85:653-661,1952) in the context of particle quantum mechanics. In particular, we construct certain background independent analogue of quantum Virasoro generators and show that in spin-zero representation they satisfy the Witt algebra with additional anomalous terms that vanish for Ricci-flat backgrounds. We also report on a new result which states that the same algebra holds true in arbitrary tensor representations as well.Comment: 8 pages, talk delivered at the Sixth International Symposium on Quantum Theory and Symmetries, University of Kentucky, July 200

Casimir-Polder attraction-repulsion crossover criterion

The mutual electromagnetic correlations between two spatially separated systems gives rise to Casimir and Casimir-Polder effect. The corresponding forces, which are generally attractive for most vacuum-separated metallic or dielectric geometries, are due to the contribution to the ground-state energy of the coupled system. We investigate here the Casimir-Polder free energy corresponding to interactions of a magnetically and electrically polarizable micro-particle with a magneto-dielectric sheet. Our semi-phenomenological study shows that such an interaction is reversibly tunable in strength and sign.The latter, particularly, is true provided we look for the exotic materials fabricated at scales between the micron and the nanometer. The crossover between attractive and repulsive behavior is found to depend on the polarizability ratio of the micro-particle and the electromagnetic impedance of the magneto-dielectric sheet.Comment: 16 pages, 3 figures. arXiv admin note: substantial text overlap with arXiv:1505.0703

Time-reversal and parity violating superconducting state of Bi_2Sr_2CaCu_20_8

The time-reversal and parity violating superconducting(SC) phase of Bi2Sr2CaCu2O8 induced by a magnetic field (B), reported by Krishana et al[K. Krishana et al, Science 277, 83 (1997)] over the limited field range of 0.6T < B < 5T, is examined starting with the model free-energy functional predicted by Laughlin [R. B. Laughlin, Physica C 234, 280 (1994)]. On the basis of entropy considerations we show that the passage from the normal to this field-driven SC state at a non-zero temperatures (T) is possible if kBT \leq \Delta 0 where the zero-temperature gap \Delta0 ~ \hbarv/lB, v is the root-mean-square velocity of the d-wave node, and lB = \surd(\hbar/eB) is the magnetic length. The restriction may be construed as setting lower limit on the required field strength at a given temperature. We find that, over the field range mentioned, the specific heat coefficient exhibits \surd B- and the B-linear dependence (Volovick effect).Comment: 2 pages,2 figure

Continuous Quantum-Classical Transitions and Measurement: A Relook

The measurement problem in quantum mechanics originates in the inability of the Schr\"odinger equation to predict definite outcomes of measurements. This is due to the lack of objectivity of the eigenstates of the measuring apparatus. Such objectivity can be achieved if a unified realist conceptual framework can be formulated in terms of wave functions and operators acting on them for both the quantum and classical domains. Such a framework was proposed and an equation for the wave function (13, 14) smoothly interpolates between the quantum and classical limits. The arguments leading to the equation are clarified in this paper, and the theory is developed further. The measurement problem in quantum mechanics is then briefly reviewed and re-examined from the point of view of this theory, and it is shown how the classical limit of the wave function of the measuring apparatus leads to a natural solution of the problem of definite measurement outcomes without the need for either collapse or pragmatic thermodynamic arguments. This is consistent with Bohr's emphasis on the primacy of classical concepts and classical measuring devices. Possible tests of the theory using low-dimensional systems such as quantum dots are indicated.Comment: 15 pages, no figure

2+1 dimensional Fermions on the low-buckled honey-comb structured lattice plane and classical Casimir-Polder force

We have calculated the Casimir-Polder interaction (CPI) of a micro-particle with a sheet on the basis of the Klimchitskaya-Mostepanenko theory. We find the result that for non-trivial susceptibility values of the sheet and micro-particle, there is crossover between attractive and repulsive behavior. The transition depends only on the impedance, involving permeability and permittivity, apart from the ratio of the film thickness and the micro-particle separation (D/d) and temperature. The approach to calculate CPI of a micro-particle with a silicene sheet involves replacing the dielectric constant of the sample by the static dielectric function obtained using the expressions for the polarization function. The silicene is described by the low-energy Liu-Yao-Feng-Ezawa (LYFE)Model Hamiltonian involving the Dirac matrices in the chiral representation obeying the Clifford algebra.We find that the collective charge excitations at zero doping, i.e., intrinsic plasmons, in this system, are absent in the Dirac limit. The valley-spin-split intrinsic plasmons, however, come into being in the case of the massive Dirac particles with characteristic frequency close to 10 THz.Furthermore, there is a longitudinal electric field induced topological insulator(TI) to spin-valley polarized metal (SVPM) transition in silicene, which is also referred to as the topological phase transition (TPT). The low-energy SVP carriers at TPT possess gap-less (mass-less) and gapped (massive) energy spectra close to the two nodal points in the Brillouin zone with maximum spin-polarization. We find that the magnitude of the Casimir-Polder force at a given ratio of the film thickness and the separation between the micro-particle and the film is greater at TPT than at the topological insulator and trivial insulator phases.Comment: 37 pages,10 figure

Reply to `No Contradictions between Bohmian and quantum mechanics'

Marchildon's claim (quant-ph/0007068) regarding Ghose's papers (quant-ph/0001024 and 0003037) is shown to be erroneous.Comment: 1 page, latex, no figure

Volume preserving multidimensional integrable systems and Nambu-Poisson Geometry

In this paper we study generalized classes of volume preserving multidimensional integrable systems via Nambu-Poisson mechanics. These integrable systems belong to the same class of dispersionless KP type equation. Hence they bear a close resemblance to the self dual Einstein equation. Recently Takasaki-Takebe provided the twistor construction of dispersionless KP and dToda type equations by using the Gindikin's pencil of two forms. In this paper we generalize this twistor construction to our systems.Comment: 15 pages, Late