Carter's constant revealed

A new formulation of Carter's constant for geodesic motion in Kerr black holes is given. It is shown that Carter's constant corresponds to the total angular momentum plus a precisely defined part which is quadratic in the linear momenta. The characterization is exact in the weak field limit obtained by letting the gravitational constant go to zero. It is suggested that the new form can be useful in current studies of the dynamics of extreme mass ratio inspiral (EMRI) systems emitting gravitational radiation.Comment: Minor changes to match published versio

Useful ‘junk': Alu RNAs in the human transcriptome

Abstract.: Alu elements are the most abundant repetitive elements in the human genome; they have amplified by retrotransposition to reach the present number of more than one million copies. Alu elements can be transcribed in two different ways, by two independent polymerases. ‘Free Alu RNAs' are transcribed by Pol III from their own promoter, while ‘embedded Alu RNAs' are transcribed by Pol II as part of protein- and non-protein-coding RNAs. Recent studies have demonstrated that both free and embedded Alu RNAs play a major role in post transcriptional regulation of gene expression, for example by affecting protein translation, alternative splicing and mRNA stability. These discoveries illustrate how a part of the ‘junk DNA' content of the human genome has been recruited to important functions in regulation of gene expressio

Noise and Full Counting Statistics of Incoherent Multiple Andreev Reflection

We present a general theory for the full counting statistics of multiple Andreev reflections in incoherent superconducting-normal-superconducting contacts. The theory, based on a stochastic path integral approach, is applied to a superconductor-double barrier system. It is found that all cumulants of the current show a pronounced subharmonic gap structure at voltages $V=2\Delta/en$. For low voltages $V\ll\Delta/e$, the counting statistics results from diffusion of multiple charges in energy space, giving the $p$th cumulant $\propto V^{2-p}$, diverging for $p\geq 3$. We show that this low-voltage result holds for a large class of incoherent superconducting-normal-superconducting contacts.Comment: 4 pages, 4 figure

The self-consistent calculation of the edge states at quantum Hall effect (QHE) based Mach-Zehnder interferometers (MZI)

The spatial distribution of the incompressible edge states (IES) is obtained for a geometry which is topologically equivalent to an electronic Mach-Zehnder interferometer, taking into account the electron-electron interactions within a Hartree type self-consistent model. The magnetic field dependence of these IES is investigated and it is found that an interference pattern may be observed if two IES merge or come very close, near the quantum point contacts. Our calculations demonstrate that, being in a quantized Hall plateau does not guarantee observing the interference behavior.Comment: EP2DS-17 Proceedings, 6 Pages, 2 Figure

Pump-probe scheme for electron-photon dynamics in hybrid conductor-cavity systems

Recent experiments on nanoscale conductors coupled to microwave cavities put in prospect transport investigations of electron-photon interplay in the deep quantum regime. Here we propose a pump-probe scheme to investigate the transient dynamics of individual electron-photon excitations in a double quantum dot-cavity system. Excitations pumped into the system decay via charge tunneling at the double dot, probed in real time. We investigate theoretically the short-time charge transfer statistics at the dot, for periodic pumping, and show that this gives access to vacuum Rabi oscillations as well as excitation dynamics in the presence of double dot dephasing and relaxation.Comment: 5 Pages, 5 figure

Electrical current noise of a beam splitter as a test of spin-entanglement

We investigate the spin entanglement in the superconductor-quantum dot system proposed by Recher, Sukhorukov and Loss, coupling it to an electronic beam-splitter. The superconductor-quantum dot entangler and the beam-splitter are treated within a unified framework and the entanglement is detected via current correlations. The state emitted by the entangler is found to be a linear superposition of non-local spin-singlets at different energies, a spin-entangled two-particle wavepacket. Colliding the two electrons in the beam-splitter, the singlet spin-state gives rise to a bunching behavior, detectable via the current correlators. The amount of bunching depends on the relative positions of the single particle levels in the quantum dots and the scattering amplitudes of the beam-splitter. The singlet spin entanglement, insensitive to orbital dephasing but suppressed by spin dephasing, is conveniently quantified via the Fano factors. It is found that the entanglement-dependent contribution to the Fano factor is of the same magnitude as the non-entangled, making an experimental detection feasible. A detailed comparison between the current correlations of the non-local spin-singlet state and other states, possibly emitted by the entangler, is performed. This provides conditions for an unambiguous identification of the non-local singlet spin entanglement.Comment: 13 pages, 8 figures, section on quantification of entanglement adde

Andreev bound states and π\pi -junction transition in a superconductor / quantum-dot / superconductor system

We study Andreev bound states and $\pi$-junction transition in a superconductor / quantum-dot / superconductor (S-QD-S) system by Green function method. We derive an equation to describe the Andreev bound states in S-QD-S system, and provide a unified understanding of the $\pi$-junction transition caused by three different mechanisms: (1) {\it Zeeman splitting.} For QD with two spin levels $E_{\uparrow}$ and $E_{\downarrow}$, we find that the surface of the Josephson current $I(\phi =\frac \pi 2)$ vs the configuration of $(E_{\uparrow},E_{\downarrow})$ exhibits interesting profile: a sharp peak around $E_{\uparrow}=E_{\downarrow}=0$; a positive ridge in the region of $E_{\uparrow}\cdot E_{\downarrow}>0$; and a {\em % negative}, flat, shallow plain in the region of $E_{\uparrow}\cdot E_{\downarrow}<0$. (2){\it \ Intra-dot interaction.} We deal with the intra-dot Coulomb interaction by Hartree-Fock approximation, and find that the system behaves as a $\pi$-junction when QD becomes a magnetic dot due to the interaction. The conditions for $\pi$-junction transition are also discussed. (3) {\it \ Non-equilibrium distribution.} We replace the Fermi distribution $f(\omega)$ by a non-equilibrium one $\frac 12[ f(\omega -V_c)+f(\omega +V_c)]$, and allow Zeeman splitting in QD where $$ The curves of $I(\phi =\frac \pi 2)$ vs $$ show the novel effect of interplay of non-equilibrium distribution with magnetization in QD.Comment: 18 pages, 8 figures, Late

Ammonia and methane emissions from dairy concentrated animal feeding operations in California, using mobile optical remote sensing

Dairy concentrated animal feeding operations (CAFOs) are significant sources of methane (CH4) and ammonia (NH3) emissions in the San Joaquin Valley, California. Optical techniques, namely, remote sensing by Solar Occultation Flux (SOF) and Mobile extractive FTIR (MeFTIR), were used to measure NH3 air column and ground air concentrations of NH3 and CH4, respectively. Campaigns were performed in May and October 2019 and covered 14 dairies located near Bakersfield and Tulare, California. NH3 and CH4 emission rates from single CAFOs averaged 101.9 \ub1 40.6 kgNH3/h and 437.7 \ub1 202.0 kgCH4/h, respectively, corresponding to emission factors (EFs) per livestock unit of 9.1 \ub1 2.7 gNH3/LU/h and 40.1 \ub1 17.8 gCH4/LU/h. The NH3 emissions had a median standard uncertainty of 17% and an expanded uncertainty (95% Confidence Interval (CI)) of 37%; meanwhile, CH4 emissions estimates had greater uncertainty, median of 25% and 53% (in the 95% CI). Decreasing NH3 to CH4 ratios and NH3 EFs from early afternoon (13:00) to early night (19:00) indicated a diurnal emission pattern with lower ammonia emissions during the night. On average, measured NH3 emissions were 28% higher when compared to daytime emission rates reported in the National Emissions Inventory (NEI) and modeled according to diurnal variation. Measured CH4 emissions were 60% higher than the rates reported in the California Air Resources Board (CARB) inventory. However, comparison with airborne measurements showed similar emission rates. This study demonstrates new air measurement methods, which can be used to quantify emissions over large areas with high spatial resolution and in a relatively short time period. These techniques bridge the gap between satellites and individual CAFOs measurements

Local and nonlocal entanglement for quasiparticle pairs induced by Andreev reflection

We investigate local and nonlocal entanglement of particle pairs induced by direct and crossed Andreev reflections at the interfaces between a superconductor and two normal conductors. It is shown theoretically that both local and nonlocal entanglement can be quantified by concurrence and detected from the violation of a Bell inequality of spin current correlators, which are determined only by normal reflection and Andreev reflection eigenvalues. There exists a one-to-one correspondence between the concurrence and the maximal Bell-CHSH parameter in the tunneling limit

Coherent current transport in wide ballistic Josephson junctions

We present an experimental and theoretical investigation of coherent current transport in wide ballistic superconductor-two dimensional electron gas-superconductor junctions. It is found experimentally that upon increasing the junction length, the subharmonic gap structure in the current-voltage characteristics is shifted to lower voltages, and the excess current at voltages much larger than the superconducting gap decreases. Applying a theory of coherent multiple Andreev reflection, we show that these observations can be explained in terms of transport through Andreev resonances.Comment: 4 pages, 4 figure