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This contribution investigates the connection between isogeometric analysis and integral equation methods for full-wave electromagnetic problems up to the low-frequency limit. The proposed spline-based integral equation method allows for an…

Computational Engineering, Finance, and Science · Computer Science 2026-05-19 Maximilian Nolte , Riccardo Torchio , Sebastian Schöps , Jürgen Dölz , Felix Wolf , Albert E. Ruehli

Ground-based observation at frequencies below 30 MHz is hindered by the ionosphere of the Earth and radio frequency interference. To map the sky at these low frequencies, we have proposed the Discovering the Sky at the Longest wavelength…

Instrumentation and Methods for Astrophysics · Physics 2021-12-22 Yuan Shi , Yidong Xu , Li Deng , Fengquan Wu , Lin Wu , Qizhi Huang , Shifan Zuo , Jingye Yan , Xuelei Chen

The 2D phase unwrapping problem seeks to recover a phase image from its observation modulo 2$\pi$, and is a crucial step in a variety of imaging applications. In particular, it is one of the most time-consuming steps in the interferometric…

Optimization and Control · Mathematics 2024-01-19 Benjamin Dubois-Taine , Roland Akiki , Alexandre d'Aspremont

Interferometric methods, renowned for their reliability and precision, play a vital role in phase imaging. Interferometry typically requires high coherence and stability between the measured and the reference beam. The presence of rapid…

Radio interferometry invariably suffers from an incomplete coverage of the spatial Fourier space, which leads to imaging artifacts. The current state-of-the-art technique is to create an image by Fourier-transforming the incomplete…

Instrumentation and Methods for Astrophysics · Physics 2024-12-19 F. Geyer , K. Schmidt , J. Kummer , M. Brüggen , H. W. Edler , D. Elsässer , F. Griese , A. Poggenpohl , L. Rustige , W. Rhode

Using a linear optical elements and post-selection, we construct an entangled polarization state of three photons in the same spatial mode. This state is analogous to a ``photon-number path entangled state'' and can be used for…

Quantum Physics · Physics 2009-11-10 M. W. Mitchell , J. S. Lundeen , A. M. Steinberg

Recovering both amplitude and phase information from a system is a fundamental goal of optical imaging. At the same time, it is crucial to operate at low photon doses to avoid altering the sample, particularly in biological applications.…

Quantum Physics · Physics 2026-01-15 Alberto Paniate , Giuseppe Ortolano , Sarika Soman , Marco Genovese , Ivano Ruo-Berchera

In order to cope with the increased data volumes generated by modern radio interferometers such as LOFAR (Low Frequency Array) or SKA (Square Kilometre Array), fast and efficient calibration algorithms are essential. Traditional radio…

Instrumentation and Methods for Astrophysics · Physics 2016-11-15 Sarod Yatawatta

In this work, the benefits of the phase fitting technique are embedded in high order discrete Lagrangian integrators. The proposed methodology creates integrators with zero phase lag in a test Lagrangian in a similar way used in phase…

Instrumentation and Methods for Astrophysics · Physics 2009-04-02 O. T. Kosmas , D. S. Vlachos

Data from radio interferometers provide a substantial challenge for statisticians. It is incomplete, noise-dominated and originates from a non-trivial measurement process. The signal is not only corrupted by imperfect measurement devices…

Instrumentation and Methods for Astrophysics · Physics 2020-11-11 Philipp Arras , Jakob Knollmüller , Henrik Junklewitz , Torsten A. Enßlin

This paper presents a point-wise divergence-free projection method for numerical approximations of photonic quasicrystals problems. The original three-dimensional quasiperiodic Maxwell's system is transformed into a periodic one in higher…

Numerical Analysis · Mathematics 2024-09-10 Zixuan Gao , Zhenli Xu , Zhiguo Yang

This paper presents a multilevel algorithm specifically designed for radio-interferometric imaging in astronomy. The proposed algorithm is used to solve the uSARA (unconstrained Sparsity Averaging Reweighting Analysis) formulation of this…

Optimization and Control · Mathematics 2024-03-21 Guillaume Lauga , Audrey Repetti , Elisa Riccietti , Nelly Pustelnik , Paulo Gonçalves , Yves Wiaux

The advent of large aperture arrays, such as the currently under construction Square Kilometer Array (SKA), allows for observing the universe in the radio-spectrum at unprecedented resolution and sensitivity. However, these telescopes…

Instrumentation and Methods for Astrophysics · Physics 2024-12-04 S. Wang , S. Prunet , S. Mignot , A. Ferrari

One of the most powerful approaches to imaging at the nanometer or subnanometer length scale is coherent diffraction imaging using X-ray sources. For amorphous (non-crystalline) samples, the raw data can be interpreted as the modulus of the…

Numerical Analysis · Mathematics 2020-04-02 Alexander Barnett , Charles L. Epstein , Leslie Greengard , Jeremy Magland

The resolution limits of classical spectroscopy can be surpassed by quantum-inspired methods leveraging the information contained in the phase of the complex electromagnetic field. Their counterpart in spatial imaging has been widely…

Optics · Physics 2024-09-02 Michał Lipka , Michał Parniak

An unbiased method for improving the resolution of astronomical images is presented. The strategy at the core of this method is to establish a linear transformation between the recorded image and an improved image at some desirable…

Astrophysics · Physics 2016-08-30 F. P. Pijpers

We introduce a loss compensation method to increase the resolution of near-field imaging with a plasmonic superlens that relies on the convolution of a high spatial frequency passband function with the object. Implementation with incoherent…

Optics · Physics 2018-01-23 Wyatt Adams , Anindya Ghoshroy , Durdu Ö. Güney

A new method recovers the phase difference of interfering wavefronts from a pattern of interference fringes, avoiding the phase discontinuity problem. The method relies on the numerical solution of one-dimensional first-order ordinary…

Optics · Physics 2024-08-01 V. Berejnov , B. Y. Rubinstein

This paper reported a general noninterferometric high-accuracy quantitative phase imaging (QPI) method for arbitrary complex valued objects. Given by a typical 4f optical configuration as the imaging system, three frames of small-window…

Image and Video Processing · Electrical Eng. & Systems 2021-05-05 Jianhui Huang , An Pan , Huiliang Jin , Guoxiang Meng , Qian Ye

A host of new low-frequency radio telescopes seek to measure the 21-cm transition of neutral hydrogen from the early universe. These telescopes have the potential to directly probe star and galaxy formation at redshifts $20 \gtrsim z…

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