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1. Active thermal cloaking and mimicking

   https://doi.org/10.1098/rspa.2020.0941  

   Cassier, Maxence; DeGiovanni, Trent; Guenneau, Sébastien; Guevara Vasquez, Fernando (May 2021, Proceedings of the Royal Society A: Mathematical, Physical and Engineering Sciences)

   null (Ed.)

   We present an active cloaking method for the parabolic heat (and mass or light diffusion) equation that can hide both objects and sources. By active, we mean that it relies on designing monopole and dipole heat source distributions on the boundary of the region to be cloaked. The same technique can be used to make a source or an object look like a different one to an observer outside the cloaked region, from the perspective of thermal measurements. Our results assume a homogeneous isotropic bulk medium and require knowledge of the source to cloak or mimic, but are in most cases independent of the object to cloak. 

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2. Boundary Integral Equation Methods for Optical Cloaking Models

   Camille Carvalho, Elsie A. (January 2022, WAVES 2022)

   Optical cloaking refers to making an object invisible by preventing the light scattering in some directions as it hits the object. There is interest in cloaking devices in radar and other applications. Developing a model to accurately capture cloaking comes with numerical challenges, however. We must determine how light propagates through a medium composed by multiple, thin layers of materials with different electromagnetic properties. In this paper we consider a multi-layered scalar transmission problem in 2D and use boundary integral equation methods to compute the field. The Kress product quadrature rule is used to approximate singular integrals evaluated on boundaries, the Boundary Regularized Integral Equation Formulation (BRIEF) method [1] with Periodic Trapezoid Rule (PTR) is employed to treat nearly singular ones (off boundaries) appearing in the representation formula. Numerical results illustrate the efficiency of this approach, which may be applied to N arbitrary smooth layers. 

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3. Far field broadband approximate cloaking for the Helmholtz equation with a Drude-Lorentz refractive index

   https://doi.org/10.1016/j.matpur.2023.12.001  

   Cakoni, Fioralba; Hovsepyan, Narek; Vogelius, Michael S (February 2024, Journal de Mathématiques Pures et Appliquées)

   This paper concerns the analysis of a passive, broadband approximate cloaking scheme for the Helmholtz equation in Rd for d = 2 or d = 3. Using ideas from transformation optics, we construct an approximate cloak by “blowing up” a small ball of radius ϵ > 0 to one of radius 1. In the anisotropic cloaking layer resulting from the “blow-up” change of variables, we incorporate a Drude-Lorentz- type model for the index of refraction, and we assume that the cloaked object is a soft (perfectly conducting) obstacle. We first show that (for any fixed ϵ) there are no real transmission eigenvalues associated with the inhomogeneity representing the cloak, which implies that the cloaking devices we have created will not yield perfect cloaking at any frequency, even for a single incident time harmonic wave. Secondly, we establish estimates on the scattered field due to an arbitrary time harmonic incident wave. These estimates show that, as ϵ approaches 0, the L2 -norm of the scattered field outside the cloak, and its far field pattern, approach 0 uniformly over any bounded band of frequencies. In other words: our scheme leads to broadband approximate cloaking for arbitrary incident time harmonic waves. 

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4. A Cloaking Mechanism to Mitigate Market Manipulation

   https://doi.org/10.24963/ijcai.2018/75  

   Wang, Xintong; Vorobeychik, Yevgeniy; Wellman, Michael P. (July 2018, Twenty-Seventh International Joint Conference on Artificial Intelligence)

   We propose a cloaking mechanism to deter spoofing, a form of manipulation in financial markets. The mechanism works by symmetrically concealing a specified number of price levels from the inside of the order book. To study the effectiveness of cloaking, we simulate markets populated with background traders and an exploiter, who strategically spoofs to profit. The traders follow two representative bidding strategies: the non-spoofable zero intelligence and the manipulable heuristic belief learning. Through empirical game-theoretic analysis across parametrically different environments, we evaluate surplus accrued by traders, and characterize the conditions under which cloaking mitigates manipulation and benefits market welfare. We further design sophisticated spoofing strategies that probe to reveal cloaked information, and find that the effort and risk exceed the gains. 

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5. Modeling broadband cloaking using 3D nano-assembled plasmonic meta-structures

   https://doi.org/10.1364/OE.395840  

   Khan, Md_Imran; Ghosh, Sayantani; Baxter, Ryan; Kim, Arnold_D (July 2020, Optics Express)

   The concept of “cloaking” an object is a very attractive one, especially in the visible (VIS) and near infra-red (NIR) regions of the electromagnetic spectrum, as that would reduce the visibility of an object to the eye. One possible route to achieving this goal is by leveraging the plasmonic property of metallic nanoparticles (NPs). We model and simulate light in the VIS and NIR scattered by a core of a homogeneous medium, covered by plasmonic cloak that is a spherical shell composed of gold nanoparticles (AuNPs). To consider realistic, scalable, and robust plasmonic cloaks that are comparable, or larger, in size to the wavelength, we introduce a multiscale simulation platform. This model uses the multiple scattering theory of Foldy and Lax to model interactions of light with AuNPs combined with the method of fundamental solutions to model interactions with the core. Numerical results of our simulations for the scattering cross-sections of core-shell composite indicate significant scattering suppression of up to 50% over a substantial portion of the desired spectral range (400 - 600 nm) for cores as large as 900 nm in diameter by a suitable combination of AuNP sizes and filling fractions of AuNPs in the shell. 

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