K.A.I.L. WIJEWARDENA GAMALATH

University of Colombo · Department of Physics

This work investigates the spectra of coloured particles radiated from Schwarzschild black holes and Kerr black holes as their mass decrease from ~1013 g to Planck mass. The emission rate formulas in terms of black hole mass, temperature, entropy, and spin are derived. The variation of spectra with time, and black hole parameters such as mass, temp...

An equation for natural frequency of a bubble oscillating in liquids is derived using the Keller-Kolodner equation by considering surface tension, viscosity, compressibility and ratios of specific heat. It is shown that the derived equation is identical to the Minnaert solution under certain conditions [1]. The simulations are done for a spherical...

A two dimensional model under uniform resistivity was studied for incompressible plasma. The dynamical equations governing the time evolution of the system was derived using basic theory in electrodynamics and fluid mechanics. A computer code to simulate the reconnection was developed with an explicit finite difference method as the discretization...

Hawking radiation is the detectable indicator of black hole evaporations. This work investigates the secondary spectra of particle radiation from black holes formed by the decay of directly emitted elementary particles into stable final products. Secondary spectra from both Schwarzschild and maximally rotating Kerr black holes are investigated. Spe...

This report presents the beautiful and cultural places in Sri Lanka attracting tourists. Democratic Socialist Republic of Sri Lanka is an island nation in South Asia, located in the Indian Ocean enrich with beautiful white sandy beaches, lush green landscapes varying from rainforests to peak wilderness sanctuaries, Buddhist monasteries and accented...

The present work discusses the conceptual and technical issues encountered in formulating a quantized theory of gravity, via the reconciliation of quantum mechanics and general relativity. Quantum effects arising in a classically defined space-time derived through a semi classical approximation are studied at length and the significance of the part...

We have shown that the Schrödinger wave equation can be explained and derived from fundamental postulates that are based on the conservation of probability, significance of measurements at infinity and nature's tendency of maintaining a system as unbiased as possible. As a reasonable measure for the local randomness, Fisher information is considere...

To explore the boundary between quantum and classical physics in the context of quantum entanglement, the particle localization via measurement induced entanglement on photons incident onto a distinguishable, massive non-interacting two-particle system was studied. The specific case of how particles acquire well defined spatial localization when li...

Motivated by recent experimental progress, we study the quantum transport properties of two-dimensional electron gases under high perpendicular magnetic fields. We use a simple tight-binding model to model the system and open-source software to simulate quantum electronic transport properties such as band structure variations and conductance-flux r...

Motivated by recent experimental progress, we study the quantum transport properties of two-dimensional electron gases under high perpendicular magnetic fields. We use a simple tight-binding model to model the system and open-source software to simulate quantum electronic transport properties such as band structure variations and conductance-flux r...

In this book, the Green’s functions applicable in studying wide variety of physical problems are introduced. The principle aim is to place the Physicist the basis of knowledge of Green’s function techniques relevant to the field of mathematics. The material covered is intended to prepare the reader for usual applications arising in physics and to f...

We have shown that the Schrödinger wave equation can be explained and derived from fundamental postulates that are based on the conservation of probability, significance of measurements at infinity and nature's tendency of maintaining a system as unbiased as possible. As a reasonable measure for the local randomness, Fisher information is considere...

Considering the analogy between classical thermodynamic parameters and black hole parameters, the four laws of thermodynamics are reinterpreted for Kerr and Kerr-Newman black holes. A simple model for the dynamic relationships was obtained by considering the surface area of the outer horizon of a Kerr and Kerr-Newman black hole as the area of a per...

To study the generation of exciton polaritons in a quantum well embedded in a semiconductor Fabry-Pérot microcavity with distributed Brag reflectors, a simple semi-classical auxiliary differential equation based model is proposed. The solutions are obtained using FDTD method considering only the excitations from ground to next excited states and on...

A model for optical switching and limiting in 2D photonic crystals of square and hexagonal lattice structures having Kerr nonlinearity is introduced with a side-coupled cavity and a waveguide. MATLAB was used to implement FDTD algorithm with perfectly matched layer boundaries. Photonic crystals formed from AlGaAs, GaAs, ZnS and Ge, rods in air were...

The incorporation of defect modes into the perfect crystal structure allows the control of the flow of light by altering the photonic bandgap and thereby can be manipulated to achieve optical switching. A model for all optical switching and limiting based on two dimensional photonic crystals is proposed for AlAs and the performance in square and he...

The incorporation of defect modes into the perfect crystal structure allows the control of the flow of light by altering the photonic bandgap and thereby can be manipulated to achieve optical switching. A model for all optical switching and limiting based on two dimensional photonic crystals is proposed for AlAs and the performance in square and he...

From the plane wave expansion method, the energy bands and density of states for optimum band gaps were obtained for diamond lattice formed from GaP, Si, InP, GaAs, InAs, Ge and BaSrTiO3 dielectrics spheres drilled in air, by changing the radius of the spheres in symmetric directions of the irreducible Brillouin zone for normalized frequency. The l...

The electronic structures and optical matrix elements of CdSe semiconductor quantum dots of near cubical, hemispherical and cylindrical shape embedded in ZnSe were calculated. Bulk Hamiltonian matrices were obtained using the empirical tight binding method including spin-orbital coupling and relativistic effects. All quantum dots were simulated in...

Incorporation of defect modes in to the perfect crystal structure allows to control the flow of light by altering the photonic bandgap and hence can be manipulated to achieve optical switching. An all optical switch based on two dimensional (2-D) photonic crystals (PC) has been proposed for GaAs and its performance in square and hexagonal lattice s...

In this paper, we study the possibility of constructing an arrival-time operator by defining a probability distribution for a quantum particle to arrive on a closed spherical surface of a spheroid, from its center. We consider a solution to this problem by integrating the probability current that flows outwards across the closed spherical's surface...

Since the dielectric contrast of photonic crystals play an important role in determining the existence of a photonic gap, the photonic energy bands, density of states of face centered cubic structured photonic crystals formed from spheres of several dielectric materials placed in air were calculated using the plane wave expansion method. A complete...

Since the dielectric contrast of photonic crystals play an important role in determining the existence of a photonic gap, the photonic energy bands, density of states of face centered cubic structured photonic crystals formed from spheres of several dielectric materials placed in air were calculated using the plane wave expansion method. A complete...

The photonic energy bands of body centered cubic photonic crystals formed from SiO2, GaP, Si, InAs, GaAs, InP, Ge and BaSrTiO3 dielectric spheres drilled in air and air holes drilled in these dielectric mediums were calculated using the plane wave expansion method. The filling factor for each dielectric material was changed until a complete energy...

The photonic energy bands of body centered cubic photonic crystals formed from SiO 2 , GaP, Si, InAs, GaAs, InP, Ge and BaSrTiO 3 dielectric spheres drilled in air and air holes drilled in these dielectric mediums were calculated using the plane wave expansion method. The filling factor for each dielectric material was changed until a complete ener...

The constrained path Monte Carlo method was used to solve the Hubbard model for strongly correlated electrons systems analytically in arbitrary dimensions for one, two and three dimensional lattices. The energy variations with electron filling, electron-electron correlation strength and time as well as the kinetic and potential energies of these sy...

The model use to study electromagnetic metamaterials in transverse electric mode was modified to study the pressure distribution in an acoustic metamaterial in a two dimensional geometry. An electromagnetic wave of 30 GHz in transverse magnetic mode at normal incidence propagating through a two dimensional isotropic semi infinite double negative me...

The model use to study electromagnetic metamaterials in transverse electric mode was modified to study the pressure distribution in an acoustic metamaterial in a two dimensional geometry. An electromagnetic wave of 30 GHz in transverse magnetic mode at normal incidence propagating through a two dimensional isotropic semi infinite double negative me...

Using the analogy between anisotropic acoustic metamaterials with magnetic metamaterials in transverse magnetic mode, an electromagnetic wave of 2 GHz n transverse magnetic mode, at normal incidence propagating through a two dimensional, anisotropic, semi infinite, double negative, metamaterial slab of 800 × 800 cells, embedded in free space, for t...

The time dependant Schrodinger equation was solved for one dimensional and two dimensional Gaussian potential wells in the presence of a strong laser field. Three laser fields Argon, Helium-Neon and Ti-Sapphire with different intensities with cosine and sine laser electric fields were used for the simulation. The Gaussian potential well get distort...

A theoretical model was developed for light pulses propagating in optical fibers by considering the nonlinear effects, the self-phase modulation and group velocity dispersion effects. The split step Fourier method was used to generate soliton pulses in a fiber composed of a glass core surrounded by a cladding layer. Gaussian and hyperbolic secant i...

A theoretical model was developed for light pulses propagating in optical fibers by considering the nonlinear effects, the self-phase modulation and group velocity dispersion effects. The split step Fourier method was used to generate soliton pulses in a fiber composed of a glass core surrounded by a cladding layer. Gaussian and hyperbolic secant i...

The three step model of high harmonic generation was used to investigate the electron behaviour in a strong laser field. The electron propagation was analyzed classically and the electron recombination with the parent atom was analyzed quantum mechanically. Three laser fields Argon with 500 nm, Helium-Neon with 632.8 nm and Ti-Sapphire with 800 nm...

The energy, current density and momentum probability densities of superconductors were studied from London, Ginzburg-Landau and BSC theories by treating cooper pair as a particle moving in a magnetic field through analytical and numerical techniques. The London and GL solution were exactly the same at the classical limit for NbN. Considering a Coop...

A mathematical model was developed to obtain the population inversion of the atoms in laser field in a laser cavity by considering the electric field in the optical cavity and the atomic states of the medium to be quantized. The master equation of the density operator of the laser field was studied analytically and numerically. Using coherent state...

A mathematical model was developed to obtain the population inversion of the atoms in laser field in a laser cavity by considering the electric field in the optical cavity and the atomic states of the medium to be quantized. The master equation of the density operator of the laser field was studied analytically and numerically. Using coherent state...

Treating the laser medium quantum mechanically and the laser electric field classically, a mathematical model was developed to study a laser field inside a single mode optical cavity by numerical and analytical techniques. The simulations for threshold population, population inversion and average population with electric field frequency for 500 kHz...

The equations of motion for the dynamic properties of spin waves in three dimensions were obtained using Heisenberg model and solved for two and three dimensional lattices analytically up to an exponential operator representation. The second order Suzuki Trotter decomposition method was extended to incorporate second nearest interaction parameters...

The equations of motion for the dynamic properties of spin waves in three dimensions were obtained using Heisenberg model and solved for two and three dimensional lattices analytically up to an exponential operator representation. The second order Suzuki Trotter decomposition method was extended to incorporate second nearest interaction parameters...

In this paper an ansatz that the anti-commutation rules hold only as integrated average over time intervals and not at every instant giving rise to a time-discrete form of Klein-Gordon equation is examined. This coarse-grained validation of the anti-commutation rules enables us to show that the relativistic energy-momentum relation holds only over...

A simple model was setup to find the mass variation over time for a Schwarzschild black hole. The temperature and entropy of a black hole was obtained from the numerically solved mass variation and the time variations of the black hole thermodynamic parameters were simulated. The mass of a given black hole reduces rapidly. The time taken for a blac...

A simple model was setup to find the mass variation over time for a Schwarzschild black hole. The temperature and entropy of a black hole was obtained from the numerically solved mass variation and the time variations of the black hole thermodynamic parameters were simulated. The mass of a given black hole reduces rapidly. The time taken for a blac...

In this paper an ansatz that the anti-commutation rules hold only as integrated average over time intervals and not at every instant giving rise to a time-discrete form of Klein-Gordon equation is examined. This coarse-grained validation of the anti-commutation rules enables us to show that the relativistic energy-momentum relation holds only over...

Using Heisenberg model, the equations of motion for the dynamic properties of spin waves in three dimensions were obtained and solved analytically up to an exponential operator representation. Second order Suzuki Trotter decomposition method with evolution operator solution was applied to obtain the numerical solutions by making it closer to real s...

Using Heisenberg model, the equations of motion for the dynamic properties of spin waves in three dimensions were obtained and solved analytically up to an exponential operator representation. Second order Suzuki Trotter decomposition method with evolution operator solution was applied to obtain the numerical solutions by making it closer to real s...

Applying plane wave expansion method to one dimensional multilayer system formed from alternating layers of GaAs and air, a defect mode was artificially introduced by removing a GaAs layer at the centre of a supercell and the band structures and mode field distributions were obtained. The defect mode normalized frequency was 0.28. The parameters fo...

The energy, current density and momentum probability densities of superconductors were studied from London, Ginzburg-Landau and BSC theories by treating cooper pair as a particle moving in a magnetic field through analytical and numerical techniques. The London and GL solution were exactly the same at the classical limit for NbN. Considering a Coop...

Applying plane wave expansion method to one dimensional multilayer system formed from alternating layers of GaAs and air, a defect mode was artificially introduced by removing a GaAs layer at the centre of a supercell and the band structures and mode field distributions were obtained. The defect mode normalized frequency was 0.28. The parameters fo...

The plane wave expansion method was implemented in modelling and simulating the band structures of three dimensional photonic crystals with FCC lattice formed from air spheres drilled in GaAs and diamond lattice formed by GaAs spheres drilled in air. Both these structures lead to a complete band gap not allowing EM waves with the frequency of the b...

The plane wave expansion method was implemented in modelling and simulating the band structures of three dimensional photonic crystals with FCC lattice formed from air spheres drilled in GaAs and diamond lattice formed by GaAs spheres drilled in air. Both these structures lead to a complete band gap not allowing EM waves with the frequency of the b...

The energy, current density and momentum probability densities of superconductors were studied from London, Ginzburg-Landau and BSC theories by treating cooper pair as a particle moving in a magnetic field through analytical and numerical techniques. The London and GL solution were exactly the same at the classical limit for NbN . Considering a Coo...

In this paper, we examine an ansatz, where anti-commutation rules hold only as integrated averages over time intervals, and not at every instant, giving rise to a time-discrete form solution to the Klein-Gordon equation. This coarse-grained validation of the anti-commutation rules enables us to show that the relativistic energy-momentum relation ho...

To investigate optical properties of Si photonic crystal waveguides, a mathematical model was set up. Finite difference time domain method was used to calculate the Maxwell’s equations numerically. For the evolution of the electromagnetic fields in the photonic crystals, simulations were done for a small lattices using Yee lattice approach. The pro...

To investigate optical properties of Si photonic crystal waveguides, a mathematical model was set up. Finite difference time domain method was used to calculate the Maxwell’s equations numerically. For the evolution of the electromagnetic fields in the photonic crystals, simulations were done for a small lattices using Yee lattice approach. The pro...

The plane wave expansion method was implemented in modelling and simulating the band structures of two dimensional photonic crystals with square, triangular and honeycomb lattices with circular, square and hexagonal dielectric rods and air holes. Complete band gaps were obtained for square lattice of square GaAs rods and honeycomb lattice of circul...

The plane wave expansion method was implemented in modelling and simulating the band structures of two dimensional photonic crystals with square, triangular and honeycomb lattices with circular, square and hexagonal dielectric rods and air holes. Complete band gaps were obtained for square lattice of square GaAs rods and honeycomb lattice of circul...

The plane wave expansion method was implemented in modelling and simulating the band structures of two dimensional photonic crystals with square, triangular and honeycomb lattices with circular, square and hexagonal dielectric rods and air holes. Complete band gaps were obtained for square lattice of square GaAs rods and honeycomb lattice of circul...

A theoretical model was developed using Green’s function with an anisotropic elastic tensor to study the strain distribution in and around three dimensional semiconductor pyramidal quantum dots formed from group IV and III-V material systems namely, Ge on Si, InAs on GaAs and InP on AlP. A larger positive strain in normal direction which tends to z...

To investigate the dynamics of a planar plasma diode system (PDS), a model based on the current density equilibrium at the interface was developed. The current densities and plasma boundary variations with the potential fields were obtained by simulating a single square pulse. The variation of an observed overshoot current density with the applied...

As the particles originating from point-like entities are associated with infinite self energies, a postulate, that the scalar-potential associated with particles are bounded by a Planck scale potential is introduced. By defining the self energy of a particle, equivalences between charge-energy and mass-energy are obtained. The electromagnetic ener...

As the particles originating from point-like entities are associated with infinite self energies, a postulate, that the scalar-potential associated with particles are bounded by a Planck scale potential is introduced. By defining the self energy of a particle, equivalences between charge-energy and mass-energy are obtained. The electromagnetic ener...

The Dirac equation consistent with the principles of quantum mechanics and the special theory of relativity, introduces a set of matrices combined with the wave function of a particle in motion to give rise to the relativistic energy-momentum relation. In this paper a new hypothesis, the wave function of a particle in motion is associated with a pa...

The Dirac equation, which provides a description of elementary particles, is consistent with both the principles of quantum mechanics and the special theory of relativity, where a set of matrices are introduced which, when combined with the wave function of a particle in motion, give rise to the relativistic energy-momentum relation. In this paper,...

The Dirac equation consistent with the principles of quantum mechanics and the special theory of relativity, introduces a set of matrices combined with the wave function of a particle in motion to give rise to the relativistic energy-momentum relation. In this paper a new hypothesis, the wave function of a particle in motion is associated with a pa...

To investigate the dynamics of a planar plasma diode system (PDS), a model based on the current density equilibrium at the interface was developed. The current densities and plasma boundary variations with the potential fields were obtained by simulating a single square pulse. The variation of an observed overshoot current density with the applied...

A theoretical model was developed using Green’s function with an anisotropic elastic tensor to study the strain distribution in and around three dimensional semiconductor pyramidal quantum dots formed from group IV and III-V material systems namely, Ge on Si, InAs on GaAs and InP on AlP. A larger positive strain in normal direction which tends to z...

For the acusto-optic interactions in liquids, an equation for the diffraction light intensity was obtained in terms of Klein Cook parameter Q. With optimized parameters for Q, incident light wave length of λ = 633 nm, sound wave length of Λ = 0.1 mm, acusto-optic interaction length L=0.1 m, and refractive index of the liquid in the range of 1 to 2,...

An approximate extension of the slender body theory was used to determine the static shape of a conically ended dielectric fluid drop in an electric field. Using induced surface charge density, hydrostatic pressure and the surface tension of the liquid with interfacial tension stresses and Maxwell electric stresses, a governing equation was obtaine...

Ion transport rate of PAFC, AFC, PEMFC, DMFC and SOFC fuel cells under the influence of an electric field and concentration gradient were evaluated for static electrolytes. AFC are the best fuel cells for higher current applications while direct methanol fuel cells DMFC are the best for lower current applications at lower temperatures. An equation...

ABSTRACT For the acusto-optic interactions in liquids, an equation for the diffraction light intensity was obtained in terms of Klein Cook parameter Q. With optimized parameters for Q, incident light wave length of �=633 nm, sound wave length of �=0.1 mm, acusto-optic interaction length L=0.1 m, and refractive index of the liquid in the range of 1...

An approximate extension of the slender body theory was used to determine the static shape of a conically ended dielectric fluid drop in an electric field. Using induced surface charge density, hydrostatic pressure and the surface tension of the liquid with interfacial tension stresses and Maxwell electric stresses, a governing equation was obtaine...

Ion transport rate of PAFC, AFC, PEMFC, DMFC and SOFC fuel cells under the influence of an electric field and concentration gradient were evaluated for static electrolytes. AFC are the best fuel cells for higher current applications while direct methanol fuel cells DMFC are the best for lower current applications at lower temperatures. An equation...

Monte Carlo method was successfully employed to study the mechanism inside a three dimensional bulk hetero-junction polymer solar cell using a model based on a novel architecture of adjustable structural parameters. The amorphous properties of the conjugated polymers were modelled to determine the operating conditions and structural properties and...

Monte Carlo method was successfully employed to study the mechanism inside a three dimensional bulk hetero-junction polymer solar cell using a model based on a novel architecture of adjustable structural parameters. The amorphous properties of the conjugated polymers were modelled to determine the operating conditions and structural properties and...

The structural, electronic, and magnetic properties of several different terminations of the BaFe2As2(001) surface are investigated by means of first-principles calculations. Analysis of the surface stability as a function of the chemical potentials reveals that the three possible terminations (As, full and half Ba coverage) can all be stabilized i...

Using a simple thermodynamic upper bound efficiency model for the conversion of solar energy into work, the best material for a converter was obtained. Modifying the existing detailed terrestrial application model of direct solar radiation to include an atmospheric transmission coefficient with cloud factors and a maximum concentration ratio, the b...