Symmetries of CMB Temperature Correlation at Large Angular Separations

A new analysis is presented of the angular correlation function $C(\Theta)$ of cosmic microwave background (CMB) temperature at large angular separation, based on published maps derived from {\sl WMAP} and {\sl Planck} satellite data, using different models of astrophysical foregrounds. It is found that using a common analysis, the results from the two satellites are very similar. In particular, it is found that previously published differences between measured values of $C(\Theta)$ near $\Theta=90^\circ$ arise mainly from different choices of masks in regions of largest Galactic emissions, and that demonstrated measurement biases are reduced by eliminating masks altogether. Maps from both satellites are shown to agree with $C(90^\circ)=0$ to within estimated statistical and systematic errors, consistent with an exact symmetry predicted in a new holographic quantum model of inflation.Comment: resubmitted to ApJ Letters, with revisions in response to referee comment

Angular correlations on causally-coherent inflationary horizons

We develop a model for correlations of cosmic microwave background anisotropy on the largest angular scales, based on standard causal geometrical relationships in slow-roll inflation. Unlike standard models based on quantized field modes, it describes perturbations with nonlocal directional coherence on spherical boundaries of causal diamonds. Causal constraints reduce the number of independent degrees of freedom, impose new angular symmetries, and eliminate cosmic variance for purely angular 2-point correlations. Distortions of causal structure from vacuum fluctuations are modeled as gravitational memory from randomly oriented outgoing and incoming gravitational null shocks, with nonlocally coherent directional displacements on curved surfaces of causal diamonds formed by standard inflationary horizons. The angular distribution is determined by axially symmetric shock displacements on circular intersections of the comoving sphere that represents the CMB photosphere with other inflationary horizons. Displacements on thin spheres at the end of inflation have a unique angular power spectrum $C_\ell$ that approximates the standard expectation on small angular scales, but differs substantially at large angular scales due to horizon curvature. For a thin sphere, the model predicts a universal angular correlation function $C(\Theta)$ with an exact ``causal shadow'' symmetry, $C(\pi/4<\Theta<3\pi/4)= 0$, and significant large-angle parity violation. We apply a rank statistic to compare models with WMAP and Planck satellite data, and find that a causally-coherent model with no shape parameters or cosmic variance agrees with the measured $C(\Theta)$ better than a large fraction ($> 0.9999$) of standard model realizations. Model-independent tests of holographic causal symmetries are proposed

A Compact Millimeter-Wavelength Fourier-Transform Spectrometer

We have constructed a Fourier-transform spectrometer (FTS) operating between 50 and 330 GHz with minimum volume (355 x260 x64 mm) and weight (13 lbs) while maximizing optical throughput (100 $\mathrm{mm}^2$ sr) and optimizing the spectral resolution (4 GHz). This FTS is designed as a polarizing Martin-Puplett interferometer with unobstructed input and output in which both input polarizations undergo interference. The instrument construction is simple with mirrors milled on the box walls and one motorized stage as the single moving element. We characterize the performance of the FTS, compare the measurements to an optical simulation, and discuss features that relate to details of the FTS design. The simulation is also used to determine the tolerance of optical alignments for the required specifications. We detail the FTS mechanical design and provide the control software as well as the analysis code online.Comment: Submitted to Applied Optics. [Copyright 2019 Optical Society of America]. Users may use, reuse, and build upon the article, or use the article for text or data mining, so long as such uses are for non-commercial purposes and appropriate attribution is maintained. All other rights are reserve

First measurements of high frequency cross-spectra from a pair of large Michelson interferometers

Measurements are reported of the cross-correlation of spectra of differential position signals from the Fermilab Holometer, a pair of co-located 39 m long, high power Michelson interferometers with flat, broadband frequency response in the MHz range. The instrument obtains sensitivity to high frequency correlated signals far exceeding any previous measurement in a broad frequency band extending beyond the 3.8 MHz inverse light crossing time of the apparatus. The dominant but uncorrelated shot noise is averaged down over $2\times 10^8$ independent spectral measurements with 381 Hz frequency resolution to obtain $2.1\times 10^{-20} \ \mathrm{m}/\sqrt{\mathrm{Hz}}$ sensitivity to stationary signals. For signal bandwidths $\Delta f > 11$ kHz, the sensitivity to strain $h$ or shear power spectral density of classical or exotic origin surpasses a milestone $PSD_{\delta h} < t_p$ where $t_p= 5.39\times 10^{-44}/\mathrm{Hz}$ is the Planck time.Comment: 5 pages, 3 figure

Interferometric Constraints on Quantum Geometrical Shear Noise Correlations

Final measurements and analysis are reported from the first-generation Holometer, the first instrument capable of measuring correlated variations in space-time position at strain noise power spectral densities smaller than a Planck time. The apparatus consists of two co-located, but independent and isolated, 40 m power-recycled Michelson interferometers, whose outputs are cross-correlated to 25 MHz. The data are sensitive to correlations of differential position across the apparatus over a broad band of frequencies up to and exceeding the inverse light crossing time, 7.6 MHz. By measuring with Planck precision the correlation of position variations at spacelike separations, the Holometer searches for faint, irreducible correlated position noise backgrounds predicted by some models of quantum space-time geometry. The first-generation optical layout is sensitive to quantum geometrical noise correlations with shear symmetry---those that can be interpreted as a fundamental noncommutativity of space-time position in orthogonal directions. General experimental constraints are placed on parameters of a set of models of spatial shear noise correlations, with a sensitivity that exceeds the Planck-scale holographic information bound on position states by a large factor. This result significantly extends the upper limits placed on models of directional noncommutativity by currently operating gravitational wave observatories.Comment: Matches the journal accepted versio

Infrared Cloud Monitoring with UCIRC2

The second generation of the Extreme Universe Space Observatory on a Super Pressure Balloon (EUSO-SPB2) is a balloon instrument that searched for ultra high energy cosmic rays (UHECRs) with energies above 1 EeV and very high energy neutrinos with energies above 1 PeV. EUSO-SPB2 consists of two telescopes: a fluorescence telescope pointed downward for the detection of UHECRs and a Cherenkov telescope toward the limb for the detection of PeV-scale showers produced by neutrino-sourced tau decay (just below the limb) and by cosmic rays (just above the limb). Clouds inside the fields of view of these telescopes--particularly that of the fluorescence telescope--reduce EUSO-SPB2's geometric aperture. As such, cloud coverage and cloud-top altitude within the field of view of the fluorescence telescope must be monitored throughout data-taking. The University of Chicago Infrared Camera (UCIRC2) monitored these clouds using two infrared cameras centered at 10 and 12 $\mu$m. By capturing images at wavelengths spanning the cloud thermal emission peak, UCIRC2 measured cloud color-temperatures and thus cloud-top altitudes. In this contribution, we provide an overview of UCIRC2, including an update on its construction and performance. We also show first results from the flight.Comment: 10 pages, 7 figures, proceedings of the 38th International Cosmic Ray Conference (ICRC 2023). arXiv admin note: substantial text overlap with arXiv:2112.09618, arXiv:1909.0266

EUSO-SPB2 Fluorescence Telescope Calibration and Field Tests

The Extreme Universe Space Observatory on a Super Pressure Balloon 2 (EUSO-SPB2), successfully launched from Wanaka, New Zealand on May 13, 2022, is a precursor for a space-based astroparticle observatory such as the Probe Of Extreme Multi-Messenger Astrophysics (POEMMA). EUSO-SPB2 flew two custom telescopes. Both have UV/UV-visible sensitivity and feature Schmidt optics. The Fluorescence Telescope (FT) measures ultra-high energy cosmic rays by looking down. The \v{C}erenkov Telescope (CT) searches for neutrino signatures by looking toward Earth's limb. The two telescopes each have a 1 m diameter entrance pupil and segmented glass mirrors that collect light from extensive air showers at the PeV and EeV-scale. Here we describe the FT telescope optics together with the results of the FT field tests at the Utah Telescope Array (TA) site from August/September 2022. The FT recorded the night sky background, lasers, and artificial point sources. The field tests included an absolute photometric calibration of the FT telescope that is compared to a piece-wise laboratory calibration

Convergence towards a European strategic culture? A constructivist framework for explaining changing norms.

The article contributes to the debate about the emergence of a European strategic culture to underpin a European Security and Defence Policy. Noting both conceptual and empirical weaknesses in the literature, the article disaggregates the concept of strategic culture and focuses on four types of norms concerning the means and ends for the use of force. The study argues that national strategic cultures are less resistant to change than commonly thought and that they have been subject to three types of learning pressures since 1989: changing threat perceptions, institutional socialization, and mediatized crisis learning. The combined effect of these mechanisms would be a process of convergence with regard to strategic norms prevalent in current EU countries. If the outlined hypotheses can be substantiated by further research the implications for ESDP are positive, especially if the EU acts cautiously in those cases which involve norms that are not yet sufficiently shared across countries