Particle physics suggests that the Universe may have undergone several phase transitions, including the well- known inflationary event associated with the separation of the strong and electroweak forces in grand unified theories. The accelerated cosmic expansion during this transition, at cosmic time t ∼ 10−36 − 10−33 s, is often viewed as an explanation for the uniformity of the CMB temperature, T , which would otherwise have required inexplicable initial conditions. With the discovery of the Higgs particle, it is now quite likely that the Universe underwent another (elec- troweak) phase transition, at T = 159.5 ± 1.5 GeV – roughly ∼ 10−11 s after the big bang. During this event, the fermions gained mass and the electric force separated from the weak force. There is currently no established explanation, however, for the apparent uniformity of the vacuum expectation value of the Higgs field which, like the uniformity in T , gives rise to its own horizon problem in standard ΛCDM cosmology. We show in this paper that a solution to the electroweak horizon problem may be found in the choice of cosmological model, and demonstrate that this issue does not exist in the alterna- tive Friedmann–Robertson–Walker cosmology known as the Rh = ct universe.

It has been known for over three decades that the monochromatic X-ray and UV luminosities in quasars are correlated, though non-linearly. This offers the possibility of using high-z quasars as standard candles for cosmological testing. In this paper, we use a recently assembled, high-quality catalogue of 1598 quasars extending all the way to redshift similar to 6, to compare the predictions of the R-h = ct and Lambda cold dark matter (Lambda CDM) cosmologies. In so doing, we affirm that the parameters characterizing the correlation depend only weakly on the chosen cosmology, and that both models account very well for the data. Unlike Lambda CDM, however, the R-h = ct model has no free parameters for this work, so the Bayesian Information Criterion favours it over Lambda CDM with a relative likelihood of similar to 88 per cent versus similar to 10 per cent. This result is consistent with the outcome of other comparative tests, many of which have shown that R-h = ct is favoured over the standard model based on a diverse range of observations.

In addition to achieving a desired freeform profile, ensuring a superb micro-roughness finish is a key factor for successful freeform optics manufacturing. We present a pseudorandom orbiting stroke-based postprocessing technique that maintains freeform optic forms, while improving small-scale surface quality. The full-aperture tool can avoid subaperture effects, and the small stroke pseudorandom tool path guarantees the match of freeform profiles while preventing the directionality of the final surface profiles. Three independent experimental studies are designed, conducted, and presented for a wide range of optics, including magnetorheological finishing-polished BK7 glass, single-point diamond turned (SPDT) poly(methyl methacrylate), and SPDT Al6061 optics. The comparison of direct measured maps on the initial and final smoothed optics verifies the form maintenance capability of the freeform optics postprocessing technology. Surface roughness measurement highlights improvements in local surface roughness and periodic toolmark errors left by the previous polishing method.

The kinematics of the MilkyWay disc as a function of age arewellmeasured at the solar radius, but have not been studied over a wider range of Galactocentric radii. Here, we measure the kinematics of mono-age, mono-[Fe/H] populations in the low and high [alpha/Fe] discs between 4 less than or similar to R less than or similar to 13 kpc and vertical bar z vertical bar less than or similar to 2 kpc using 65 719 stars in common between APOGEE DR14 and Gaia DR2 for which we estimate ages using a Bayesian neural network model trained on asteroseismic ages. We determine the vertical and radial velocity dispersions, finding that the low and high [alpha/Fe] discs display markedly different age-velocity dispersion relations (AVRs) and shapes sigma(z)/sigma(R). The high [alpha/Fe] disc has roughly flat AVRs and constant sigma(z)/sigma(R) = 0.64 +/- 0.04, whereas the low [alpha/Fe] disc has large variations in this ratio that positively correlate with the mean orbital radius of the population at fixed age. The high [alpha/Fe] disc component's flat AVRs and constant sigma(z)/sigma(R) clearly indicate an entirely different heating history. Outer disc populations also have flatter radial AVRs than those in the inner disc, likely due to thewaning effect of spiral arms. Our detailedmeasurements ofAVRs and sigma(z)/sigma(R) across the disc indicate that low [alpha/Fe], inner disc (R less than or similar to 10 kpc) stellar populations are likely dynamically heated by both giant molecular clouds and spiral arms, while the observed trends for outer disc populations require a significant contribution from another heating mechanism such as satellite perturbations. We also find that outer disc populations have slightly positive mean vertical and radial velocities likely because they are part of the warped disc.

Dark-field illumination is a simple yet elegant imaging technique that can be used to detect the presence of particles on a specular surface. However, the sensitivity of dark-field illumination to initial conditions affects its repeatability. This is problematic in cases where automation is desired. We present an improvement to the current method of using a modulation field that relies on phase calculations rather than intensity. As a result, we obtain a computational method that is insensitive to noise and provides clearly defined particle information, allowing a global threshold to be set for autonomous measurement purposes. After introducing the theory behind our method, we present experimental results for various scenarios and compare them to those obtained using the dark-field approach.

A linear field of view (FOV) K-mirror system used for image derotation is presented as a case example for how to leverage freeform surfaces in dynamic optical configuration design. As the K-mirror rotates about the optical axis, points in the FOV sample the surface at distinct locations, allowing for highly local control of the system aberrations. This methodology is distinct from the typical benefits associated with freeform surfaces, and as such broadens the uses of freeform optics into the category of systems that exhibit changing optical configurations. We show that compared to an on-axis or off-axis conic design, the freeform surface has better distortion correction abilities. Furthermore, a real pupil is generated by the K-mirror system and analyzed for uniformity. The design ideas presented for the K-mirror are discussed in the context of astronomical applications, where systems may benefit from these techniques.

Thermal X-ray emission from rotation-powered pulsars is believed to originate from localized ‘hotspots’ on the stellar surface occurring where large-scale currents from the magnetosphere return to heat the atmosphere. Light-curve modelling has primarily been limited to simple models, such as circular antipodal emitting regions with constant temperature. We calculate more realistic temperature distributions within the polar caps, taking advantage of recent advances in magnetospheric theory, and we consider their effect on the predicted light curves. The emitting regions are non-circular even for a pure dipole magnetic field, and the inclusion of an aligned magnetic quadrupole moment introduces a north–south asymmetry. As the quadrupole moment is increased, one hotspot grows in size before becoming a thin ring surrounding the star. For the pure dipole case, moving to the more realistic model changes the light curves by 5−10percent for millisecond pulsars, helping to quantify the systematic uncertainty present in current dipolar models. Including the quadrupole gives considerable freedom in generating more complex light curves. We explore whether these simple dipole+quadrupole models can account for the qualitative features of the light curve of PSR J0437−4715.

In this paper, we probe the hot, post-shock gas component of quasar-driven winds through the thermal SunyaevZeldovich (tSZ) effect. Combining data sets from the Atacama Cosmology Telescope, the Herschel Space Observatory, and the Very Large Array, we measure average spectral energy distributions of 109 829 optically selected, radio quiet quasars from 1.4 to 3000 GHz in six redshift bins between 0.3 < z < 3.5. We model the emission components in the radio and far-infrared, plus a spectral distortion from the tSZ effect. At z > 1.91, we measure the tSZ effect at 3.8 sigma significance with an amplitude corresponding to a total thermal energy of 3.1 x 10(60) erg. If this energy is due to virialized gas, then our measurement implies quasar host halo masses are similar to 6 x 10(12) h(-1) M-circle dot. Alternatively, if the host dark matter halo masses are similar to 2 x 10(12) h(-1) M-circle dot as some measurements suggest, then we measure a >90 per?cent excess in the thermal energy over that expected due to virialization. If the measured SZ effect is primarily due to hot bubbles from quasar-driven winds, we find that (5(-1.3)(+1.2)) per?cent of the quasar bolometric luminosity couples to the intergalactic medium over a fiducial quasar lifetime of 100 Myr. An additional source of tSZ may be correlated structure, and further work is required to separate the contributions. At z <= 1.91, we detect emission at 95 and 148 GHz that is in excess of thermal dust and optically thin synchrotron emission. We investigate potential sources of this excess emission, finding that CO line emission and an additional optically thick synchrotron component are the most viable candidates.

The streaming instability (SI) is a mechanism to aerodynamically concentrate solids in protoplanetary disks and facilitate the formation of planetesimals. Recent numerical modeling efforts have demonstrated the increasing complexity of the initial mass distribution of planetesimals. To better constrain this distribution, we conduct SI simulations including self-gravity with the highest resolution hitherto. To subsequently identify all of the self-bound clumps, we develop a new clump-finding tool, Planetesimal Analyzer. We then apply a maximum likelihood estimator to fit a suite of parameterized models with different levels of complexity to the simulated mass distribution. To determine which models are best-fitting and statistically robust, we apply three model selection criteria with different complexity penalties. We find that the initial mass distribution of clumps is not universal regarding both the functional forms and parameter values. Our model selection criteria prefer models different from those previously considered in the literature. Fits to multi-segment power-law models break to a steeper distribution above masses close to those of 100 km collapsed planetesimals, similar to observed size distributions in the Kuiper Belt. We find evidence for a turnover at the low-mass end of the planetesimal mass distribution in our high-resolution run. Such a turnover is expected for gravitational collapse, but had not previously been reported.

The streaming instability concentrates solid particles in protoplanetary disks, leading to gravitational collapse into planetesimals. Despite its key role in producing particle clumping and determining critical length scales in the instability's linear regime, the influence of the disk's radial pressure gradient on planetesimal properties has not been examined in detail. Here, we use streaming instability simulations that include particle self-gravity to study how the planetesimal initial mass function depends on the radial pressure gradient. Fitting our results to a power law, dN/dM(p) proportional to M-p(-p), we find that a single value p approximate to 1.6 describes simulations in which the pressure gradient varies by greater than or similar to 2. An exponentially truncated power law provides a significantly better fit, with a low-mass slope of p' approximate to 1.3 that weakly depends on the pressure gradient. The characteristic truncation mass is found to be similar to M-G = 4 pi(5)G(2)Sigma(3)(p)/Omega(4). We exclude the cubic dependence of the characteristic mass with pressure gradient suggested by linear considerations, finding instead a linear scaling. These results strengthen the case for a streaming-derived initial mass function that depends at most weakly on the aerodynamic properties of the disk and participating solids. A simulation initialized with zero pressure gradient-which is not subject to the streaming instability-also yields a top-heavy mass function but with modest evidence for a different shape. We discuss the consistency of the theoretically predicted mass function with observations of Kuiper Belt planetesimals, and describe implications for models of early-stage planet formation.