Researcher:
Oflaz, Neslihan

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PhD Student

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Neslihan

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Oflaz

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Oflaz, Neslihan

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2014 - 20195

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Researcher Of Publications: search.filters.isAuthorOfPublication.3db38669-8233-47b9-992f-7bd45c20f34e

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    Unidirectional reflection and invisibility in nonlinear media with an incoherent nonlinearity
    (Elsevier Science Bv, 2017) N/A; Department of Mathematics; N/A; Mostafazadeh, Ali; Oflaz, Neslihan; Faculty Member; PhD Student; Department of Mathematics; College of Sciences; Graduate School of Sciences and Engineering; 4231; N/A
    We give explicit criteria for the reflectionlessness, transparency, and invisibility of a finite-range potential in the presence of an incoherent (intensity-dependent) nonlinearity that is confined to the range of the potential. This allows us to conduct a systematic study of the effects of such a nonlinearity on a locally periodic class of finite-range potentials that display perturbative unidirectional invisibility. We use our general results to examine the effects of a weak Kerr nonlinearity on the behavior of these potentials and show that the presence of nonlinearity destroys the unidirectional invisibility of these potentials. If the strength of the Kerr nonlinearity is so weak that the first-order perturbation theory is reliable, the presence of nonlinearity does not affect the unidirectional reflectionlessness and transmission reciprocity of the potential. We show that the expected violation of the latter is a second order perturbative effect.
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    PublicationOpen Access
    Accelerated expansion of the Universe in a higher dimensional modified gravity with Euler-Poincaré terms
    (Institute of Physics (IOP) Publishing, 2015) Akarsu, Özgür; Department of Physics; Dereli, Tekin; Oflaz, Neslihan; PhD Student; Department of Physics; College of Sciences; 201358; N/A
    A higher dimensional modified gravity theory with an action that includes dimensionally continued Euler-Poincare forms up to second order in curvatures is considered. The variational field equations are derived. Matter in the Universe at large scales is modeled by a fluid satisfying an equation of state with dimensional dichotomy. We study solutions that describe higher dimensional steady state cosmologies with constant volume for which the three dimensional external space is expanding at an accelerated rate while the (compact) internal space is contracting. We showed that the second order Euler-Poincare term in the constructions of higher dimensional steady state cosmologies could be crucial.
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    Accelerating anisotropic cosmologies in Brans-Dicke gravity coupled to a mass-varying vector field
    (Institute of Physics (IOP) Publishing, 2014) Department of Physics; Akarsu, Özgür; Dereli, Tekin; Oflaz, Neslihan; PhD Student; Department of Physics; College of Sciences; N/A; 201358; N/A
    The field equations of Brans-Dicke gravity coupled to a mass-varying vector field are derived. Anisotropic cosmological solutions with a locally rotationally symmetric Bianchi type I metric and time-dependent scalar and electric vector fields are studied. A particular class of exact solutions for which all the variable parameters have a power-law time dependence is given. The universe expands with a constant expansion anisotropy within this class of solutions. We show that the accelerating expansion is driven by the scalar field and the electric vector field can be interpreted as an anisotropic dark matter source.
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    Blow-up solutions of Helmholtz equation for a Kerr slab with a complex linear and nonlinear permittivity
    (American Institute of Physics (AIP) Publishing, 2019) Department of Mathematics; Department of Physics; Kalantarov, Varga; Mostafazadeh, Ali; Oflaz, Neslihan; Faculty Member; Faculty Member; PhD Student; Department of Mathematics; Department of Physics; College of Sciences; Graduate School of Sciences and Engineering; N/A; 4231; N/A
    We show that the Helmholtz equation describing the propagation of transverse electric waves in a Kerr slab with a complex linear permittivity epsilon(l) and a complex Kerr coefficient sigma admits blow-up solutions, provided that the real part of a is negative, i.e., the slab is defocusing. This result applies to homogeneous as well as inhomogeneous Kerr slabs if epsilon(l) and sigma are continuous functions of the transverse coordinate, and the real part of sigma is bounded above by a negative number. It shows that a recently reported nonlinear optical amplification effect, which relies on the existence of blow-up solutions, persists the presence of losses and transverse inhomogeneities.
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    Scattering due to geometry: case of a spinless particle moving on an asymptotically flat embedded surface
    (American Physical Society (APS), 2018) Ahmady, Mehrdad; Department of Mathematics; Department of Physics; Oflaz, Neslihan; Mostafazadeh, Ali; PhD Student; Faculty Member; Department of Mathematics; Department of Physics; College of Sciences; Graduate School of Sciences and Engineering; N/A; 4231
    A nonrelativistic quantum mechanical particle moving freely on a curved surface feels the effect of the nontrivial geometry of the surface through the kinetic part of the Hamiltonian, which is proportional to the Laplace-Beltrami operator, and a geometric potential, which is a linear combination of the mean and Gaussian curvatures of the surface. The coefficients of these terms cannot be uniquely determined by general principles of quantum mechanics but enter the calculation of various physical quantities. We examine their contribution to the geometric scattering of a scalar particle moving on an asymptotically flat embedded surface. In particular, having in mind the possibility of an experimental realization of the geometric scattering in a low-density electron gas formed on a bumped surface, we determine the scattering amplitude for arbitrary choices of the curvature coefficients for a surface with global or local cylindrical symmetry. We also examine the effect of perturbations that violate this symmetry and consider surfaces involving bumps that form a lattice.