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Quantum limit on time measurement in a gravitational field
No full textRestricted Access. An open-access version is available at arXiv.org (one of the alternative locations)Good clocks are of importance both to fundamental physics and for applications in astronomy, metrology and global positioning systems. In a recent technological breakthrough, researchers at NIST have been able to achieve a stability of one part in 1018 using an ytterbium clock. This naturally raises the question of whether there are fundamental limits to time keeping. In this article we point out that gravity and quantum mechanics set a fundamental limit on the fractional frequency uncertainty of clocks. This limit comes from a combination of the uncertainty relation, the gravitational redshift and the relativistic time dilation effect. For example, a single ion aluminium clock in a terrestrial gravitational field cannot achieve a fractional frequency uncertainty better than one part in 1022. This fundamental limit explores the interaction between gravity and quantum mechanics on a laboratory scale
Phase-sensitive radial extraction and mass spectrometry of trapped ions in a compact geometry
No full textRestricted Access.The detection of trapped atomic and molecular ions of rubidium, by extraction, from our thin-wire electrode-modified spherical Paul trap, is discussed in detail. The compact geometry poses serious challenges and constraints for efficient extraction and reliable detection of ions. The solution to the dual challenge of counting the trapped ions with minimum pileup loss as well as detection that permits reliable mass spectroscopy is experimentally implemented. The details of the ion extraction process are understood by numerical simulation. The experimental and numerical data are compared and found to be in close agreement. The reliability of the technique for future, multi-species experiments, is established, and possible improvements are discussed
Enhancing access to audio and video collections of Raman research institute library through digitization
No full textOpen Access, Proceedings of Library and Information Services in Astronomy (LISA) VII on Open Science: At the Frontiers of Librarianship, held at INAF, Astronomical Observatory of Capodimonte, Naples, Italy. From 17th to 20th June 2014, Edited by A. Holl et alThe library at the Raman Research (RRI) began digitization of its audio and video (AV) collections starting in the year 2000 with the intent to enhance the accessibility of these items. AV collections in their original format are problematic since they are vulnerable to physical damage and decay in uncontrolled climate conditions. Further, as AV formats have changed over the years, older formats become unreadable due to the fact that the equipment needed to view such materials is obsolete or no longer available. This paper will show how RRI has taken multiple measures to address these various problems. At first, catalogue records were enhanced with additional metadata, but this did not sufficiently enhance access. Next, the library converted the AV materials to CDs, but this format also posed various problems, as CDs are susceptible to damage and do not allow for multiple simultaneous use. Finally, the RRI library digitized AV materials and placed them on the RRI intranet and the web for wider accessibilit
Giant radio galaxies – II. Tracers of large-scale structure
No full textOpen AccessWe have carried out optical spectroscopy with the Anglo-Australian Telescope for 24 726 objects surrounding a sample of 19 giant radio galaxies (GRGs) selected to have redshifts in the range 0.05–0.15 and projected linear sizes from 0.8 to 3.2 Mpc. Such radio galaxies are ideal candidates to study the warm-hot intergalactic medium because their radio lobes extend beyond the interstellar medium and haloes of their host galaxies, and into the tenuous intergalactic medium. We were able to measure redshifts for 9076 galaxies. Radio imaging of each GRG, including high-sensitivity, wide-band radio observations from the Australia Telescope Compact Array for 12 GRGs and host optical spectra (presented in a previous paper), is used in conjunction with the surrounding galaxy redshifts to trace large-scale structure. We find that the mean galaxy number overdensity in volumes of ∼700 Mpc3 near the GRG host galaxies is ∼70 indicating an overdense but non-virialized environment. A Fourier component analysis is used to quantify the anisotropy in the surrounding galaxy distribution. For GRGs with radio components offset from the radio axis, there is a clear influence of the environment with lobes appearing to be deflected away from overdensities in the surrounding medium. Furthermore, the GRG lobes tend to be normal to the plane defined by the galaxy neighbourhood close to the host. This indicates the tendency for lobes to grow to giant sizes in directions that avoid dense regions on both small and large scales
Long way to go: how outflows from large galaxies propagate through the hot halo gas
No full textOpen AccessUsing hydrodynamic simulations, we study the mass-loss due to supernova-driven outflows from Milky Way type disc galaxies, paying particular attention to the effect of the extended hot halo gas. We find that the total mass-loss at inner radii scales roughly linearly with total mass of stars formed, and that the mass loading factor at the virial radius can be several times its value at inner radii because of the swept up hot halo gas. The temperature distribution of the outflowing material in the inner region (∼10 kpc) is bimodal in nature, peaking at 105 K and 106.5 K, responsible for optical and X-ray emission, respectively. The contribution of cold/warm gas with temperature ≤105.5 K to the outflow rate within 10 kpc is ≈0.3–0.5. The warm mass loading factor, η3e5 (T ≤ 3 × 105 K) is related to the mass loading factor at the virial radius (ηv) as ηv ≈ 25 η3e5 (SFR/M⊙ yr−1)−0.15 for a baryon fraction of 0.1 and a starburst period of 50 Myr. We also discuss the effect of multiple bursts that are separated by both short and long periods. The outflow speed at the virial radius is close to the sound speed in the hot halo, ≲ 200 km s−1. We identify two ‘sequences’ of outflowing cold gas at small scales: a fast (≈500 km s−1) sequence, driven by the unshocked free-wind; and a slow sequence (≈± 100 km s−1) at the conical interface of the superwind and the hot halo
Joint measurability, steering, and entropic uncertainty
No full textOpen Access.There has been a surge of research activity recently on the role of joint measurability of unsharp observables in nonlocal features, viz., violation of Bell inequality and EPR steering. Here, we investigate the entropic uncertainty relation for a pair of noncommuting observables (of Alice's system) when an entangled quantum memory of Bob is restricted to record outcomes of jointly measurable positive operator valued measures. We show that with this imposed constraint of joint measurability at Bob's end, the entropic uncertainties associated with Alice's measurement outcomes—conditioned by the results registered at Bob's end—obey an entropic steering inequality. Thus, Bob's nonsteerability is intrinsically linked to his inability to predict the outcomes of Alice's pair of noncommuting observables with better precision, even when they share an entangled state. As a further consequence, we prove that in the joint measurability regime, the quantum advantage envisaged for the construction of security proofs in quantum key distribution is lost
Crystal structure of bis-(4-meth-oxy-phenyl) malonate.
No full textOpen AccessThe complete mol-ecule of the title compound, C17H16O6, is generated by crystallographic twofold symmetry, with the central methyl-ene C atom lying on the rotation axis. The carbonyl O atom is disordered over two adjacent positions in a 0.63 (3):0.37 (3) ratio and the dihedral angle between the benzene rings in the two halves of the mol-ecule is 79.31 (12)°. In the crystal, mol-ecules are connected by C-H⋯O hydrogen bonds, generating (110) sheets. Very weak intra-sheet C-H⋯π inter-actions are also observed
Diffusion in a potential landscape with stochastic resetting
No full textOpen AccessThe steady state of a Brownian particle diffusing in an arbitrary potential under the stochastic resetting mechanism has been studied. We show that there are different classes of nonequilibrium steady states depending on the nature of the potential. In the stable potential landscape, the system attains a well-defined steady state; however, the existence of the steady state for the unstable landscape is constrained. We have also investigated the transient properties of the propagator towards the steady state under the stochastic resetting mechanism. Finally, we have done numerical simulations to verify our analytical results