Ambiguous Modes Research Articles

Pure-mode correlation functions for cosmic shear and application to KiDS-1000

One probe for systematic effects in gravitational lensing surveys is the presence of so-called B modes in the cosmic shear two-point correlation functions, ξ±(ϑ), since lensing is expected to produce only E-mode shear. Furthermore, there exist ambiguous modes that cannot uniquely be assigned to either E- or B-mode shear. In this paper we derive explicit equations for the pure-mode shear correlation functions, ξ±E/B(ϑ), and their ambiguous components, ξ±amb(ϑ), that can be derived from the measured ξ±(ϑ) on a finite angular interval, ϑmin ≤ ϑ ≤ ϑmax, such that ξ±(ϑ) can be decomposed uniquely into pure-mode functions as ξ+ = ξ+E+ξ+B+ξ+amb and ξ− = ξ−E−ξ−B+ξ−amb. The derivation is obtained by defining a new set of Complete Orthogonal Sets of E and B mode-separating Integrals (COSEBIs), for which explicit relations are obtained and which yields a smaller covariance between COSEBI modes. We derive the relation between ξ±E/B/amb and the underlying E- and B-mode power spectra. The pure-mode correlation functions can provide a diagnostic of systematics in configuration space. We then apply our results to Scinet LIght Cone Simulations (SLICS) and the Kilo-Degree Survey (KiDS-1000) cosmic shear data, calculate the new COSEBIs and the pure-mode correlation functions, as well as the corresponding covariances, and show that the new statistics fit equally well to the best fitting cosmological model as the previous KiDS-1000 analysis and recover the same level of (insignificant) B modes. We also consider in some detail the ambiguous modes at the first- and second-order level, finding some surprising results. For example, the shear field of a point mass, when cut along a line through the center, cannot be ascribed uniquely to an E-mode shear and is thus ambiguous; additionally, the shear correlation functions resulting from a random ensemble of point masses, when measured over a finite angular range, correspond to an ambiguous mode.

High-Resolution Wide-Swath Ambiguous Synthetic Aperture Radar Modes for Ship Monitoring

This paper proposes two high-resolution, wide-swath synthetic aperture radar (SAR) acquisition modes for ship monitoring that tolerate ambiguities and do not require digital beamforming. Both modes, referred to as the low pulse repetition frequency (PRF) and the staggered (high PRF) ambiguous modes, make use of a wide elevation beam, which can be obtained by phase tapering. The first mode is a conventional stripmap mode with a PRF much lower than the nominal Doppler bandwidth, allowing for the imaging of a large swath, because the ships’ azimuth ambiguities can be recognized as they appear at known positions. The second mode exploits a continuous variation of the pulse repetition interval, with a mean PRF greater than the nominal Doppler bandwidth as the range ambiguities of the ships are smeared and are unlikely to determine false alarms. Both modes are thought to operate in open sea surveillance, monitoring Exclusive Economic Zones or international waters. Examples of implementation of both modes for TerraSAR-X show that ground swaths of 120 km or 240 km can be mapped with 2 m2 resolution, ensuring outstanding detection performance even for small ships. The importance of resolution over noise and ambiguity level was highlighted by a comparison with ScanSAR modes that image comparable swaths with better noise and ambiguity levels but coarser resolutions.

Layer parity dependent Raman-active modes and crystal symmetry in ReS2

${\mathrm{ReS}}_{2}$, a group VII transition metal dichalcogenide (TMD), bears immense prospect in optoelectronic, thermoelectric, catalytic, and energy storage applications. Its distorted structure and significant in-plane anisotropy introduce extra degree of freedom but, on the other hand, make it challenging to determine the absolute characteristics of the material. Here, through experimental and theoretical analysis, we present additional phonon modes in the Raman spectrum of layered ${\mathrm{ReS}}_{2}$ which, in literature, are regarded as ambiguous modes arising due to either double resonance or defects. However, we demonstrate that these additional phonon modes arise from the crystal symmetry. This report proves the most followed notion of a layer-independent monolayer (ML)-based unit cell of ${\mathrm{ReS}}_{2}$ to be misleading. We further demonstrate that the observed additional phonon modes are driven by unique layer-dependent variations in the crystal symmetry. Moreover, layer-parity-dependent splitting of ${E}_{g}^{1}$ mode and inversion symmetry breaking are discussed in detail. Such layer-dependent features have remained largely ignored in the literature. The results presented here may open new avenues for the application of this material and resolve several contradictions in its properties including the significance of stacking order, layer-dependent crystal symmetry, and shifting of Raman modes.

Who’s afraid of Virginia Woolf? Readers’ responses to experimental techniques of speech, thought and consciousness presentation in Woolf’sTo the LighthouseandMrs Dalloway

Woolf’s work has been the object of several studies concerned with her experimental use of techniques of speech, thought and consciousness presentation. These investigated the way in which different perspectives coexist and alternate in her writing, suggesting that the use of such techniques often results in ambiguous perspective shifts. However, there is hardly any empirical evidence as to whether readers experience difficulty while reading her narratives as a result of these narrative techniques. This article examines empirically readers’ responses to extracts from Woolf’s two major novels – To the Lighthouse and Mrs Dalloway – to provide evidence for whether Woolf’s techniques for the presentation of characters’ voices, thoughts and perspectives represent a challenge for readers. To achieve this, a mixed-methods approach that combines a stylistic analysis with a detailed questionnaire has been employed. Selected extracts that were hypothesised to be complex due to the presence of free indirect style and/or interior monologue were modified by substituting these with less ambiguous modes of consciousness presentation, such as direct speech or direct thought. Readers’ responses to the modified and unmodified versions of the same extracts were compared: results show that the presence of free indirect style and/or interior monologue increases the number of perspectives identified by readers, suggesting that this technique increases the texts’ difficulty, laying a more solid ground for future investigations.

Wiener filtering and pure $\mathcal {E}/\mathcal {B}$ decomposition of CMB maps with anisotropic correlated noise

ABSTRACTWe present an augmented version of our dual messenger algorithm for spin field reconstruction on the sphere, while accounting for highly non-trivial and realistic noise models such as modulated correlated noise. We also describe an optimization method for the estimation of noise covariance from Monte Carlo simulations. Using simulated Planck polarized cosmic microwave background (CMB) maps as a showcase, we demonstrate the capabilities of the algorithm in reconstructing pure $\mathcal {E}$ and $\mathcal {B}$ maps, guaranteed to be free from ambiguous modes resulting from the leakage or coupling issue that plagues conventional methods of $\mathcal {E}/\mathcal {B}$ separation. Due to its high speed execution, coupled with lenient memory requirements, the algorithm can be optimized in exact global Bayesian analyses of state-of-the-art CMB data for a statistically optimal separation of pure $\mathcal {E}$ and $\mathcal {B}$ modes. Our algorithm, therefore, has a potentially key role in the data analysis of high-resolution and high-sensitivity CMB data, especially with the range of upcoming CMB experiments tailored for the detection of the elusive primordial $\mathcal {B}$-mode signal.

As If It Was Ours All Along: Precarious Belonging, Jewish Habitus and the Materialisation of Conversion in Israel

ABSTRACTMost scholarship on Jewish conversion in Israel emphasises the precarious entanglement between the process and the politics of the Jewish State. This article, instead, unpacks the uncertain modes of converts’ belonging from an unexplored yet central angle – that of a Jewish habitus. I trace the challenging apprenticeship that aspiring converts undertake in developing a Jewish habitus, and the deeply ambiguous modes of belonging that such an apprenticeship shapes. By evaluating ethnographically the discourses and practices that aspiring converts are introduced to, this article detects how attempts to help them adopt the Jewish insiders’ embodied dispositions and materially embedded engagements simultaneously, albeit inadvertently, mark them as profoundly outsiders. The case study of Jewish conversion in Israel offers a compelling example with which to consider the conceptual links between belonging, habitus and conversion.

Pure E and B polarization maps via Wiener filtering

In order to draw scientific conclusions from observations of cosmic microwave background (CMB) polarization, it is necessary to separate the contributions of the $E$ and $B$ components of the data. For data with incomplete sky coverage, there are ambiguous modes, which can be sourced by either $E$ or $B$ signals. Techniques exist for producing ``pure'' $E$ and $B$ maps, which are guaranteed to be free of cross-contamination, although the standard method, which involves constructing an eigenbasis, has a high computational cost. We show that such pure maps can be thought of as resulting from the application of a Wiener filter to the data. This perspective leads to far more efficient methods of producing pure maps. Moreover, by expressing the idea of purification in the general framework of Wiener filtering (i.e., maximization of a posterior probability), it leads to a variety of generalizations of the notion of pure $E$ and $B$ maps, e.g., accounting for noise or other contaminants in the data as well as correlations with temperature anisotropy.

Observing the “Local Globalness” of Policy Transfer in Education

This article contributes to a growing body of research on global policy transfer and flows in education, arguing that a large number of such research has too often viewed nation-states as uniform policy containers, focusing mainly on national-level policy changes or using binary understandings of reform adaptation versus reform resistance. Consequently, it often neglected the internal complexities of nation-states, which include ambiguous modes of ongoing global-local “recontextualization,” local meanings of reforms, but also (changing) influence of national and local actors who may operate as policy “brokers.” Using data from an empirical case study on the German state Bremen, we illustrate how global-local policy dynamics played out locally in sequences of school structural reforms between 2002 and 2010. Hereby, we combine the theory of path dependency with the conceptualization of policy fields to better understand the various complexities and dynamics within a multilevel educational reform movement.

Wavelet reconstruction ofEandBmodes for CMB polarization and cosmic shear analyses

We present new methods for mapping the curl-free (E-mode) and divergence-free (B-mode) components of spin 2 signals using spin directional wavelets. Our methods are equally applicable to measurements of the polarisation of the cosmic microwave background (CMB) and the shear of galaxy shapes due to weak gravitational lensing. We derive pseudo and pure wavelet estimators, where E-B mixing arising due to incomplete sky coverage is suppressed in wavelet space using scale- and orientation-dependent masking and weighting schemes. In the case of the pure estimator, ambiguous modes (which have vanishing curl and divergence simultaneously on the incomplete sky) are also cancelled. On simulations, we demonstrate the improvement (i.e., reduction in leakage) provided by our wavelet space estimators over standard harmonic space approaches. Our new methods can be directly interfaced in a coherent and computationally-efficient manner with component separation or feature extraction techniques that also exploit wavelets.

Conceptualizing Semi-Legality in Migration Research

What is semi-legality, and why does it offer a viable alternative to the legality–illegality binary divide? Semi-legality, as a heuristic device, is useful to frame the various “in-between” statuses and not resorting to illegality every time ambiguities arise as this casts the net of potential fraud far too wide. It could be viewed as a multidimensional space where migrants' formal relationships with the state interact with their various forms of agency toward the law. As a sensitizing theoretical perspective, it helps to explain why many neoliberal regimes, which claim that law and order are the main features distinguishing them from others, actually engage in perpetuating the legally ambiguous modes of incorporation. Delineating the conditions of semi-legality, I use data from 360 qualitative interviews with migrants in four European countries. I discuss: (1) “incomplete” responses to regularization programs (amnesties) – de facto fulfilling the legalization conditions, yet facing barriers to formally (de jure) corroborate this; (2) balancing between the temporality of residence in various EU countries—under-staying in some and overstaying in others; and (3) the nexus with employment—where migrants' residence in a country is lawful, but their work exceeds the restrictions permitted by their visas.

Beyond the Veil: Indeterminacy and Iconoclasm in the Art of Robert Hayden, Janet Kozachek, and Tom Feelings

Robert Hayden employs innovative modes of signification to unveil and expose race-based violence in United States. In Night, Death, Mississippi (1966) he defies bildverbot (1) traditions, or customary injunction against representing sacred or, in secular times, secret. This policy pertains to what must not be shown because it lies reach of representation (traditionally, God or Shoah) and also applies to what must not be shown because its portrayal undermines hegemonic ideologies that maintain and naturalize systems of oppression (as in phenomena of lynching and slavery). Some topics are designated unspeakable, beyond veil, or simply lack first-hand witnesses. Yet, this barred access or knowledge gap due to iconoclastic tendencies in culture does not inhibit a poet accustomed to poetry's mode of meaning by indirection. While we live in a time of relative freedom of speech and expression, vestiges of prohibition against depicting unrepresentable subject matter have led writers and artists to seek alternate aesthetic strategies that insist on historical and contemporary realities even as they dismantle conventional realism. Hayden's innovative portrayal of ostensibly obscene (ob scaena) matter of a death by lynching works according to ambiguous modes that depend on materiality of medium (language), rather than materiality of desecrated body itself. By treating language as a revelatory concrete substance--a clay of sounds, a stack of stanzas, a shifting web of syntax ruled and unruled--Hayden calls attention to his creative activity, and by extension, to hidden or forbidden subject matter as well. Thus, medium's material qualities anchor poem as does space/time referent: U.S.A., in mid 1960s. From this fixed point, poet then raises metaphysical questions about society and human suffering. In defiance of restrictions against using art to signify certain categories of experience, Hayden tears away rhetorical veil that falls over episodes too terrible to recount (to use a common collocation from slave narratives), employing a poetics of indeterminacy that both tempers and intensifies truth with its rhetorical power. The poet's insistence on subject matter, examining a generalized episode of a recurring event, serves as a call to witness for both those who follow his line of vision and those who avert their eyes. Dispersing perspective among at least four entities, Hayden offers a polyphony of internal and articulated voices that stage a quasi-narrative spanning past, present and future experience, both actual and imaginary. The trope of veil occupies a central position in U.S. literary history, due in part to ways W. E. B. Du Bois uses it in The Souls of Black Folk (1903) as a sign of mourning, an instrument of separation or concealment, and a marker of prophecy. Werner Sollors explicates Old Testament references to demonstrate metaphor's function to separate Afro-Americans from American culture at large but also [to give] them a more profound vision and higher destiny (49; qtd. in Gates and Oliver xxviii): Du Bois imaginatively adapted two biblical images of veil as a division within Temple [Exodus 26.33] and as cover that divinely inspired Moses wore when he came back from Mount Sinai and spoke to people [Exodus 34.33-35]. (49) Hayden transposes this metaphoric configuration into an aesthetic strategy as he writes Night, Death, Mississippi, using language to obscure and reveal in delicate tones of lament that ultimately solidify protest nature of his poem. Hayden twice evokes notion of iconoclasm, literally the breaking of icons, in his essays on Harlem Renaissance-era activism (Prose 46) and on later aesthetic innovations (Recent Poetry 69). According to Hayden, Harlem Renaissance artists shattered inauthentic images of Black experience, asserting their own new depictions in place of old stereotypes. …

Efficient decomposition of cosmic microwave background polarization maps into pureE, pureB, and ambiguous components

Separation of the $B$ component of a cosmic microwave background (CMB) polarization map from the much larger $E$ component is an essential step in CMB polarimetry. For a map with incomplete sky coverage, this separation is necessarily hampered by the presence of ambiguous modes which could be either $E$ or $B$ modes. I present an efficient pixel-space algorithm for removing the ambiguous modes and separating the map into pure $E$ and $B$ components. The method, which works for arbitrary geometries, does not involve generating a complete basis of such modes and scales the cube of the number of pixels on the boundary of the map.

General solution to theE−Bmixing problem

We derive a general ansatz for optimizing pseudo-${C}_{\ensuremath{\ell}}$ estimators used to measure cosmic microwave background anisotropy power spectra, and apply it to the recently proposed pure pseudo-${C}_{\ensuremath{\ell}}$ formalism, to obtain an estimator which achieves near-optimal $B$-mode power spectrum errors for any specified noise distribution while minimizing leakage from ambiguous modes. Our technique should be relevant for upcoming cosmic microwave background polarization experiments searching for $B$-mode polarization. We compare our technique both to the theoretical limits based on a full Fisher matrix calculation and to the standard pseudo-${C}_{\ensuremath{\ell}}$ technique. We demonstrate it by applying it to a fiducial survey with realistic inhomogeneous noise, complex boundaries, point source masking, and a noise level comparable to what is expected for next-generation experiments ($\ensuremath{\sim}5.75\text{ }\text{ }\ensuremath{\mu}\mathrm{K}\mathrm{\text{\ensuremath{-}}}\mathrm{arcmin}$). For such an experiment our technique could improve the constraints on the amplitude of a gravity wave background by over a factor of 10 compared to what could be obtained using ordinary pseudo-${C}_{\ensuremath{\ell}}$, coming quite close to saturating the theoretical limit. Constraints on the amplitude of the lensing $B$-modes are improved by about a factor of 3.

HarmonicE/Bdecomposition for CMB polarization maps

The full sky cosmic microwave background polarization field can be decomposed into ``electric'' (E) and ``magnetic'' (B) components that are signatures of distinct physical processes. We give a general construction that achieves separation of E and B modes on arbitrary sections of the sky at the expense of increasing the noise. When E modes are present on all scales the separation of all of the B signal is no longer possible: there are inevitably ambiguous modes that cannot be separated. We discuss the practicality of performing $E/B$ decomposition on large scales with realistic nonsymmetric sky cuts, and show that separation on large scales is possible by retaining only the well supported modes. The large scale modes potentially contain a great deal of useful information, and $E/B$ separation at the level of the map is essential for clean detection of B without confusion from cosmic variance due to the E signal. We give simple matrix manipulations for creating pure E and B maps of the large scale signal for general sky cuts. We demonstrate that the method works well in a realistic case and give estimates of the performance with data from the Planck satellite. In the Appendix we discuss the simple analytic case of an azimuthally symmetric cut, and show that exact $E/B$ separation is possible on an azimuthally symmetric cut with a finite number of nonintersecting circular cuts around foreground sources.

E/Bdecomposition of finite pixelized CMB maps

Separation of the E and B components of a microwave background polarization map or a weak lensing map is an essential step in extracting science from it, but when the map covers only part of the sky and/or is pixelized, this decomposition cannot be done perfectly. We present a method for decomposing an arbitrary sky map into a sum of three orthogonal components that we term ``pure E,'' ``pure B,'' and ``ambiguous.'' The fluctuations in the pure E and B maps are due only to the E and B power spectra, respectively, whereas the source of those in the ambiguous map is completely indeterminate. This method is useful both for providing intuition for experimental design and for analyzing data sets in practice. We show how to find orthonormal bases for all three components in terms of bi-Laplacian eigenfunctions, thus providing a type of polarized signal-to-noise eigenmodes that simultaneously separate both angular scale and polarization type. The number of pure and ambiguous modes probing a characteristic angular scale \ensuremath{\theta} scales as the map area over ${\ensuremath{\theta}}^{2}$ and as the map boundary length over \ensuremath{\theta}, respectively. This implies that fairly round maps (with short perimeters for a given area) will yield the most efficient $E/B$ decomposition and also that the fraction of the information lost to ambiguous modes grows towards larger angular scales. For real-world data analysis, we present a simple matrix eigenvalue method for calculating nearly pure E and B modes in pixelized maps. We find that the dominant source of leakage between E and B is aliasing of small-scale power caused by the pixelization, essentially since derivatives are involved. This problem can be eliminated by heavily oversampling the map, but is exacerbated by the fact that the E power spectrum is expected to be much larger than the B power spectrum and by the extremely blue power spectrum that cosmic microwave background polarization is expected to have. We found that a factor of 2 to 3 more pixels are needed in a polarization map to achieve the same level of contamination by aliased power than in a temperature map. Oversampling is therefore much more important for the polarized case than for the unpolarized case, which should be reflected in experimental design.

The Estimation of Ambiguous Change in 4WS Control System Using Failure Detection Filter

This paper presents a new method for estimating the ambiguous change in a 4WS control system using failure detection filter. This filter is designed to discriminate ambiguous failure modes in the control system by processing output errors between sensors and an observer. The result of the experiments using a 4WS vehicle revealed that the filter can estimate the failures of the sensors and the actuator with high accuracy. The effects of lateral wind and other disturbances on the filter were also clarified.