Negatively charged nitrogen-vacancy centres in diamond are promising quantum magnetic field sensors. Laser threshold magnetometry has been a theoretical approach for the improvement of NV-centre ensemble sensitivity via increased signal strength and
magnetic field contrast. In this work we experimentally demonstrate laser threshold magnetometry. We use a macroscopic high-finesse laser cavity containing a highly NV-doped and low absorbing diamond gain medium that is pumped at 532nm and resonantly seeded at 710nm. This enables amplification of the signal power by stimulated emission of 64%. We show the magnetic-field dependency of the amplification and thus, demonstrate magnetic-field dependent stimulated emission from an NV-centre ensemble. This emission shows a record contrast of 33% and a maximum output power in the mW regime. These advantages of coherent read-out of NV-centres pave the way for novel cavity and laser applications of quantum defects as well as diamond NV magnetic field sensors with significantly improved sensitivity for the health, research and mining sectors.
Context: The current sample of known brown dwarfs (BDs) around FGK-stars is only of the order of a hundred. The ongoing ESA mission Gaia has already collected its nominal 5 yr of mission data and might operate up to 10 yr. Aims: Using detailed simu
lations, we estimate the number of BDs that could be discovered by Gaia astrometry, radial velocity, and photometric transits around main sequence (V) and subgiants (IV) FGK host stars for a 5 and 10-yr mission. Methods: Using a robust $Delta chi^2$ statistic we analyse the BD companion detectability from the Besanc{c}on Galaxy population synthesis model complemented by Gaia DR2 data for the bright end, using the latest Gaia performance and scanning law, and literature-based BD-parameter distributions. Results: We report here reliable detection numbers ($Delta chi^2$>50) for a 5-yr [10-yr] mission. Astrometry alone yields 28,000-42,000 [45,000-55,000] detections out to several hundred pc [>kiloparsec], with the majority around G magnitude 14-15 [14-16] and P>200 d. Gaia radial velocity time series allow detection of 830-1100 [1500-1900] mainly massive BDs (55-80 M_J), most having P <10 d. Systems with at least 3 photometric transits (S/N>3) are expected for 720-1100 [1400-2300] BDs, averaging at 4-5 [5-6] transits per source. Overlap of astrometric and radial velocity detection yield 370-410 [870-950] candidates, transit and radial velocity 17-27 [35-56], and transit and astrometric detection 1-3 [4-6]. Conclusions: Though above numbers have +/- 50% uncertainty due to the uncertain occurrence rate and period distribution of BDs around FGK host stars, Gaia detections will number in the tens-of-thousands, enlarging the current sample by at least two orders of magnitude, allowing to investigate the BD fraction and orbital architectures as a function of host stellar parameters in greater detail than every before.
We have analyzed the parsec-scale jet kinematics of 447 bright radio-loud AGN, based on 15 GHz VLBA data obtained between 1994 August 31 and 2019 August 4. We present new total intensity and linear polarization maps obtained between 2017 January 1 to
2019 August 4 for 143 of these AGN. We tracked 1923 bright features for five or more epochs in 419 jets. A majority (60%) of the well-sampled jet features show either accelerated or non-radial motion. In 47 jets there is at least one non-accelerating feature with an unusually slow apparent speed. Most of the jets show variations of 10 to 50 deg in their inner jet position angle (PA) over time, although the overall distribution has a continuous tail out to 200 deg. AGN with SEDs peaked at lower frequencies tend to have more variable PAs, with BL Lacs being less variable than quasars. The Fermi LAT gamma-ray associated AGN also tend to have more variable PAs than the non-LAT AGN in our sample. We attribute these trends to smaller viewing angles for the lower spectral peaked and LAT-associated jets. We identified 13 AGN where multiple features emerge over decade-long periods at systematically increasing or decreasing PAs. Since the ejected features do not fill the entire jet cross-section, this behavior is indicative of a precessing flow instability near the jet base. Although some jets show indications of oscillatory PA evolution, we claim no bona fide cases of periodicity since the fitted periods are comparable to the total VLBA time coverage.
Modern electric power systems have witnessed rapidly increasing penetration of renewable energy, storage, electrical vehicles and various demand response resources. The electric infrastructure planning is thus facing more challenges due to the variab
ility and uncertainties arising from the diverse new resources. This study aims to develop a multistage and multiscale stochastic mixed integer programming (MM-SMIP) model to capture both the coarse-temporal-scale uncertainties, such as investment cost and long-run demand stochasticity, and fine-temporal-scale uncertainties, such as hourly renewable energy output and electricity demand uncertainties, for the power system capacity expansion problem. To be applied to a real power system, the resulting model will lead to extremely large-scale mixed integer programming problems, which suffer not only the well-known curse of dimensionality, but also computational difficulties with a vast number of integer variables at each stage. In addressing such challenges associated with the MM-SMIP model, we propose a nested cross decomposition algorithm that consists of two layers of decomposition, that is, the Dantzig-Wolfe decomposition and L-shaped decomposition. The algorithm exhibits promising computational performance under our numerical study, and is especially amenable to parallel computing, which will also be demonstrated through the computational results.
Multi-wavelength simultaneous observations are essential to the constraints on the origin of fast radio bursts (FRBs). However, it is a significant observational challenge due to the nature of FRBs as transients with a radio millisecond duration, whi
ch occur randomly in the sky regardless of time and position. Here, we report the search for short-time fast optical bursts in the GWAC archived data associated with FRB 20181130B, which were detected by the Five Hundred Meter Spherical Radio Telescope (FAST) and recently reported. No new credible sources were detected in all single GWAC images with an exposure time of 10 s, including image with coverage of the expected arrival time in optical wavelength by taking the high dispersion measurements into account. Our results provide a limiting magnitude of 15.43$pm0.04$ mag in R band, corresponding to a flux density of 1.66 Jy or 8.35 mag in AB system by assuming that the duration of the optical band is similar to that of the radio band of about 10 ms. This limiting magnitude makes the spectral index of $alpha<0.367$ from optical to radio wavelength. The possible existence of longer duration optical emission was also investigated with an upper limits of 0.33 Jy (10.10 mag), 1.74 mJy (15.80 mag) and 0.16 mJy (18.39 mag) for the duration of 50 ms, 10 s and 6060 s, respectively. This undetected scenario could be partially attributed to the shallow detection capability, as well as the high inferred distance of FRB 20181130B and the low fluence in radio wavelength. The future detectability of optical flashes associated with nearby and bright FRBs are also discussed in this paper.
Let $dot A$ be a densely defined, closed, symmetric operator in the complex, separable Hilbert space $mathcal{H}$ with equal deficiency indices and denote by $mathcal{N}_i = ker big(big(dot Abig)^* - i I_{mathcal{H}}big)$, $dim , (mathcal{N}_i)=kin m
athbb{N} cup {infty}$, the associated deficiency subspace of $dot A$ . If $A$ denotes a self-adjoint extension of $dot A$ in $mathcal{H}$, the Donoghue $m$-operator $M_{A,mathcal{N}_i}^{Do} (, cdot ,)$ in $mathcal{N}_i$ associated with the pair $(A,mathcal{N}_i)$ is given by [ M_{A,mathcal{N}_i}^{Do}(z)=zI_{mathcal{N}_i} + (z^2+1) P_{mathcal{N}_i} (A - z I_{mathcal{H}})^{-1} P_{mathcal{N}_i} bigvert_{mathcal{N}_i},, quad zin mathbb{C} backslash mathbb{R}, ] with $I_{mathcal{N}_i}$ the identity operator in $mathcal{N}_i$, and $P_{mathcal{N}_i}$ the orthogonal projection in $mathcal{H}$ onto $mathcal{N}_i$. Assuming the standard local integrability hypotheses on the coefficients $p, q,r$, we study all self-adjoint realizations corresponding to the differential expression [ tau=frac{1}{r(x)}left[-frac{d}{dx}p(x)frac{d}{dx} + q(x)right] , text{ for a.e. $xin(a,b) subseteq mathbb{R}$,} ] in $L^2((a,b); rdx)$, and, as the principal aim of this paper, systematically construct the associated Donoghue $m$-functions (resp., $2 times 2$ matrices) in all cases where $tau$ is in the limit circle case at least at one interval endpoint $a$ or $b$.
We reconstruct spectra of secondary x-rays generated from a 500 MeV - 2 GeV laser plasma electron accelerator. A compact (7.5 $times$ 7.5 $times$ 15 cm), modular x-ray calorimeter made of alternating layers of absorbing materials and imaging plates r
ecords the single-shot x-ray depth-energy distribution. X-rays range from few-MeV inverse Compton scattered x-rays to $sim$100 MeV average bremsstrahlung energies and are characterized individually by the same calorimeter detector. Geant4 simulations of energy deposition from mono-energetic x-rays in the stack generate an energy-vs-depth response matrix for the given stack configuration. A fast, iterative reconstruction algorithm based on analytic models of inverse Compton scattering and bremsstrahlung photon energy distributions then unfolds x-ray spectra in $sim10$ seconds.
The flare-associated stellar coronal mass ejection (CME) in solar-like and late type stars is quite essential for the habitability of an exoplanet. In this paper, we report detection of flare-associated CMEs in two M-dwarfs, thanks to the high cadenc
e survey carried out by the Ground Wide-angle Camera system and the fast photometric and spectroscopic follow-ups. The flare energy in $R-$band is determined to be $1.6times10^{35} mathrm{erg}$ and $8.1times10^{33} mathrm{erg}$ based on the modeling of their light curves. The time-resolved spectroscopyic observations start at about 20 and 40 minutes after the trigger in both cases. The large projected maximum velocity of $sim500-700 mathrm{km s^{-1}}$ suggests that the high velocity wing of their H$alpha$ emission lines are most likely resulted from a CME event in both stars, after excluding the possibility of chromospheric evaporation and coronal rain. The masses of the CMEs are estimated to be $1.5-4.5times10^{19} mathrm{g}$ and $7.1times10^{18} mathrm{g}$.
Hexagonal rare-earth ferrite RFeO$_3$ family represents a unique class of multiferroics exhibiting weak ferromagnetism, and a strong coupling between magnetism and structural trimerization is predicted. However, the hexagonal structure for RFeO$_3$ r
emains metastable in conventional condition. We have succeeded in stabilizing the hexagonal structure of polycrystalline YbFeO$_3$ by partial Sc substitution of Yb. Using bulk magnetometry and neutron diffraction, we find that Yb$_{0.42}$Sc$_{0.58}$FeO$_3$ orders into a canted antiferromagnetic state with the Neel temperature $T_N$ ~ 165 K, below which the $Fe^{3+}$ moments form the triangular configuration in the $ab$-plane and their in-plane projections are parallel to the [100] axis, consistent with magnetic space group $P$6$_{3}$$cm$. It is determined that the spin-canting is aligned along the $c$-axis, giving rise to the weak ferromagnetism. Furthermore, the $Fe^{3+}$ moments reorient toward a new direction below reorientation temperature $T_R$ ~ 40 K, satisfying magnetic subgroup $P$6$_{3}$, while the $Yb^{3+}$ moments order independently and ferrimagnetically along the $c$-axis at the characteristic temperature $T_{Yb}$ ~ 15 K. Interestingly, reproducible modulation of electric polarization induced by magnetic field at low temperature is achieved, suggesting that the delicate structural distortion associated with two-up/one-down buckling of the Yb/Sc-planes and tilting of the FeO$_5$ bipyramids may mediate the coupling between ferroelectric and magnetic orders under magnetic field. The present work represents a substantial progress to search for high-temperature multiferroics in hexagonal ferrites and related materials.
Coherence distillation is a central topic of the resource theory of coherence and various coherence distillation protocols were proposed. In this paper, we investigate the optimal probabilistic coherence distillation protocol, whose aim is to transfo
rm a coherent state into a set of $n$-level maximally coherent states by using strictly incoherent operations. Specifically, we accomplish this protocol by presenting an analytical expression for the maximal average distillable coherence for a general state and constructing the corresponding operation achieving this bound. Our protocol is a universal protocol since it can be applied to any coherence measure.
