There is, I think, something ethereal about i —the square root of minus one. I remember first hearing about it at school. It seemed an odd beast at that time—an intruder hovering on the edge of reality.

Usually familiarity dulls this sense of the bizarre, but in the case of i it was the reverse: over the years the sense of its surreal nature intensified. It seemed that it was impossible to write mathematics that described the real world in …

I and i

Deposits of clastic carbonate-dominated (calciclastic) sedimentary slope systems in the rock record have been identified mostly as linearly-consistent carbonate apron deposits, even though most ancient clastic carbonate slope deposits fit the submarine fan systems better. Calciclastic submarine fans are consequently rarely described and are poorly understood. Subsequently, very little is known especially in mud-dominated calciclastic submarine fan systems. Presented in this study are a sedimentological core and petrographic characterisation of samples from eleven boreholes from the Lower Carboniferous of Bowland Basin (Northwest England) that reveals a >250 m thick calciturbidite complex deposited in a calciclastic submarine fan setting. Seven facies are recognised from core and thin section characterisation and are grouped into three carbonate turbidite sequences. They include: 1) Calciturbidites, comprising mostly of highto low-density, wavy-laminated bioclast-rich facies; 2) low-density densite mudstones which are characterised by planar laminated and unlaminated muddominated facies; and 3) Calcidebrites which are muddy or hyper-concentrated debrisflow deposits occurring as poorly-sorted, chaotic, mud-supported floatstones. These

Phd by thesis

On August 17, 2017 at 12∶41:04 UTC the Advanced LIGO and Advanced Virgo gravitational-wave detectors made their first observation of a binary neutron star inspiral. The signal, GW170817, was detected with a combined signal-to-noise ratio of 32.4 and a false-alarm-rate estimate of less than one per 8.0×10^{4}  years. We infer the component masses of the binary to be between 0.86 and 2.26  M_{⊙}, in agreement with masses of known neutron stars. Restricting the component spins to the range inferred in binary neutron stars, we find the component masses to be in the range 1.17-1.60  M_{⊙}, with the total mass of the system 2.74_{-0.01}^{+0.04}M_{⊙}. The source was localized within a sky region of 28  deg^{2} (90% probability) and had a luminosity distance of 40_{-14}^{+8}  Mpc, the closest and most precisely localized gravitational-wave signal yet. The association with the γ-ray burst GRB 170817A, detected by Fermi-GBM 1.7 s after the coalescence, corroborates the hypothesis of a neutron star merger and provides the first direct evidence of a link between these mergers and short γ-ray bursts. Subsequent identification of transient counterparts across the electromagnetic spectrum in the same location further supports the interpretation of this event as a neutron star merger. This unprecedented joint gravitational and electromagnetic observation provides insight into astrophysics, dense matter, gravitation, and cosmology.

/pdf/gw170817-observation-of-gravitational-waves-from-a-binary-q2x9byg981.pdf

GW170817: observation of gravitational waves from a binary neutron star inspiral

On September 14, 2015 at 09:50:45 UTC the two detectors of the Laser Interferometer Gravitational-Wave Observatory simultaneously observed a transient gravitational-wave signal. The signal sweeps upwards in frequency from 35 to 250 Hz with a peak gravitational-wave strain of 1.0×10(-21). It matches the waveform predicted by general relativity for the inspiral and merger of a pair of black holes and the ringdown of the resulting single black hole. The signal was observed with a matched-filter signal-to-noise ratio of 24 and a false alarm rate estimated to be less than 1 event per 203,000 years, equivalent to a significance greater than 5.1σ. The source lies at a luminosity distance of 410(-180)(+160)  Mpc corresponding to a redshift z=0.09(-0.04)(+0.03). In the source frame, the initial black hole masses are 36(-4)(+5)M⊙ and 29(-4)(+4)M⊙, and the final black hole mass is 62(-4)(+4)M⊙, with 3.0(-0.5)(+0.5)M⊙c(2) radiated in gravitational waves. All uncertainties define 90% credible intervals. These observations demonstrate the existence of binary stellar-mass black hole systems. This is the first direct detection of gravitational waves and the first observation of a binary black hole merger.

/pdf/the-observation-of-gravitational-waves-from-a-binary-black-58srpupgg9.pdf

The Observation of Gravitational Waves from a Binary Black Hole Merger

Many physically motivated extensions to general relativity (GR) predict significant deviations at energies present in massive neutron stars. We report the measurement of a 2.01 \(\pm \) 0.04 solar mass (M\(_\odot \)) pulsar in a 2.46-h orbit around a 0.172 \(\pm \) 0.003 M\(_\odot \) white dwarf. The high pulsar mass and the compact orbit make this system a sensitive laboratory of a previously untested strong-field gravity regime. Thus far, the observed orbital decay agrees with GR, supporting its validity even for the extreme conditions present in the system. The resulting constraints on deviations support the use of GR-based templates for ground-based gravitational wave detection experiments. Additionally, the system strengthens recent constraints on the properties of dense matter and provides novel insight to binary stellar astrophysics and pulsar recycling.

/pdf/a-massive-pulsar-in-a-compact-relativistic-binary-4fslj44n2n.pdf

A massive pulsar in a compact relativistic binary

We examine how the uncertainties involved in supernova dynamics, as well as in nuclear data inputs, affect the νp-process in the neutrino-driven winds. For the supernova dynamics, we find that the wind termination by the preceding dense ejecta shell, as well as the electron fraction (Y e,3; at 3 × 109 K), plays a crucial role. A wind termination within the temperature range of (1.5-3) × 109 K greatly enhances the efficiency of the νp-process. This implies that the early wind phase, when the innermost layer of the preceding supernova ejecta is still ~200-1000 km from the center, is most relevant to the νp-process. The outflows with Y e,3 = 0.52-0.60 result in the production of the p-nuclei up to A = 108 with interesting amounts. Furthermore, the p-nuclei up to A = 152 can be produced if Y e,3 = 0.65 is achieved. For the nuclear data inputs, we test the sensitivity to the rates relevant to the breakout from the p-p chain region (A < 12), to the (n, p) rates on heavy nuclei, and to the nuclear masses along the νp-process pathway. We find that a small variation of the rates of triple-α and of the (n, p) reaction on 56Ni leads to a substantial change in the p-nuclei production. We also find that 96Pd (N = 50) on the νp-process path plays a role as a second seed nucleus for the production of heavier p-nuclei. The uncertainty in the nuclear mass of 82Zr can lead to a factor of two reduction in the abundance of the p-isotope 84Sr.

/pdf/uncertainties-in-the-np-process-supernova-dynamics-versus-32s3fw42qs.pdf

Uncertainties in the νp-process: supernova dynamics versus nuclear physics

Remnants of neutron-star mergers are essentially massive, hot, differentially rotating neutron stars, which are initially strongly oscillating. As such they represent a unique probe for high-density matter because the oscillations are detectable via gravitational-wave measurements and are strongly dependent on the equation of state. The impact of the equation of state for instance is apparent in the frequency of the dominant oscillation mode of the remnant. For a fixed total binary mass a tight relation between the dominant postmerger oscillation frequency and the radii of nonrotating neutron stars exists. Inferring observationally the dominant postmerger frequency thus determines neutron star radii with high accuracy of the order of a few hundred meters. By considering symmetric and asymmetric binaries of the same chirp mass, we show that the knowledge of the binary mass ratio is not critical for this kind of radius measurements. We perform simulations which show that initial intrinsic neutron star rotation is unlikely to affect this method of constraining the high-density equation of state. We also summarize different possibilities about how the postmerger gravitational-wave emission can be employed to deduce the maximum mass of nonrotating neutron stars. We clarify the nature of the three most prominent features of the postmerger gravitational-wave spectrum and argue that the merger remnant can be considered to be a single, isolated, self-gravitating object that can be described by concepts of asteroseismology. We sketch how the consideration of the strength of secondary gravitational-wave peaks leads to a classification scheme of the gravitational-wave emission and postmerger dynamics. The understanding of the different mechanisms shaping the gravitational-wave signal yields a physically motivated analytic model of the gravitational-wave emission, which may form the basis for template-based gravitational-wave data analysis. We explore the observational consequences of a scenario of two families of compact stars including hadronic and quark matter stars. We find that this scenario leaves a distinctive imprint on the postmerger gravitational-wave signal. In particular, a strong discontinuity in the dominant postmerger frequency as function of the total mass will be a strong indication for two families of compact stars.

Exploring properties of high-density matter through remnants of neutron-star mergers

The first full-scale three-dimensional core-collapse supernova (SN) simulations with sophisticated neutrino transport show pronounced effects of the standing accretion shock instability (SASI) for two high-mass progenitors (20 and 27 M([Symbol: see text])). In a low-mass progenitor (11.2 M([Symbol: see text])), large-scale convection is the dominant nonradial hydrodynamic instability in the postshock accretion layer. The SASI-associated modulation of the neutrino signal (80 Hz in our two examples) will be clearly detectable in IceCube or the future Hyper-Kamiokande detector, depending on progenitor properties, distance, and observer location relative to the main SASI sloshing direction. The neutrino signal from the next galactic SN can, therefore, diagnose the nature of the hydrodynamic instability.

Neutrino Signature of Supernova Hydrodynamical Instabilities in Three Dimensions

Based on new developments in the understanding of supernovae (SNe) as gravitational-wave (GW) sources we estimate the GW background from all cosmic SNe. For a broad range of frequencies around 1 Hz, this background is crudely comparable to the GW background expected from standard inflationary models. While our estimate remains uncertain within several orders of magnitude, the SN GW background may become detectable by second-generation space-based interferometers such as the proposed Big Bang Observatory (BBO). By the same token, the SN GWs may become a foreground for searches of the inflationary GWs, in particular, for sub-Hz frequencies where the SN background is Gaussian and where the BBO will be most sensitive. SN simulations lasting far beyond the usual cutoff of about 1 s are needed for more robust predictions in the sub-Hz frequency band. An even larger GW background can arise from a hypothetical early population of massive stars, although their GW source strength as well as their abundance are currently poorly understood.

/pdf/stochastic-gravitational-wave-background-from-cosmological-3fnbrcxdnd.pdf

Stochastic Gravitational Wave Background from Cosmological Supernovae

We re-examine the very stringent limits on the axion mass based on the strength and duration of the neutrino signal from SN 1987A, in the light of new measurements of the axial-vector coupling strength of nucleons, possible suppression of axion emission due to many-body effects, and additional emission processes involving pions. The suppression of axion emission due to nucleon spin fluctuations induced by many-body effects degrades previous limits by a factor of about 2. Emission processes involving thermal pions can strengthen the limits by a factor of 3-4 within a perturbative treatment that neglects saturation of nucleon spin fluctuations. Inclusion of saturation effects, however, tends to make the limits less dependent on pion abundances. The resulting axion mass limit also depends on the precise couplings of the axion and ranges from 0.5x10**(-3) eV to 6x10**(-3) eV.

/pdf/a-fresh-look-at-axions-and-sn-1987a-1tj68mfooh.pdf

Hans-Thomas Janka

Papers

Uncertainties in the νp-process: supernova dynamics versus nuclear physics

Exploring properties of high-density matter through remnants of neutron-star mergers

Neutrino Signature of Supernova Hydrodynamical Instabilities in Three Dimensions

Stochastic Gravitational Wave Background from Cosmological Supernovae

A Fresh Look at Axions and SN 1987A