On 2017 August 17 a binary neutron star coalescence candidate (later designated GW170817) with merger time 12:41:04 UTC was observed through gravitational waves by the Advanced LIGO and Advanced Virgo detectors. The Fermi Gamma-ray Burst Monitor independently detected a gamma-ray burst (GRB 170817A) with a time delay of ∼ 1.7 s with respect to the merger time. From the gravitational-wave signal, the source was initially localized to a sky region of 31 deg2 at a luminosity distance of 40 − 8 + 8 Mpc and with component masses consistent with neutron stars. The component masses were later measured to be in the range 0.86 to 2.26 M ⊙ . An extensive observing campaign was launched across the electromagnetic spectrum leading to the discovery of a bright optical transient (SSS17a, now with the IAU identification of AT 2017gfo) in NGC 4993 (at ∼ 40 Mpc ) less than 11 hours after the merger by the One-Meter, Two Hemisphere (1M2H) team using the 1 m Swope Telescope. The optical transient was independently detected by multiple teams within an hour. Subsequent observations targeted the object and its environment. Early ultraviolet observations revealed a blue transient that faded within 48 hours. Optical and infrared observations showed a redward evolution over ∼10 days. Following early non-detections, X-ray and radio emission were discovered at the transient’s position ∼ 9 and ∼ 16 days, respectively, after the merger. Both the X-ray and radio emission likely arise from a physical process that is distinct from the one that generates the UV/optical/near-infrared emission. No ultra-high-energy gamma-rays and no neutrino candidates consistent with the source were found in follow-up searches. These observations support the hypothesis that GW170817 was produced by the merger of two neutron stars in NGC 4993 followed by a short gamma-ray burst (GRB 170817A) and a kilonova/macronova powered by the radioactive decay of r-process nuclei synthesized in the ejecta.

We study a system of interacting spinless fermions in one dimension which, in the absence of interactions, reduces to the Kitaev chain [A. Yu Kitaev, Phys.-Usp. 44, 131 (2001)]. In the noninteracting case, a signal of topological order appears as zero-energy modes localized near the edges. We show that the exact ground states can be obtained analytically even in the presence of nearestneighbor repulsive interactions when the on-site (chemical) potential is tuned to a particular function of the other parameters. As with the non-interacting case, the obtained ground states are two-fold degenerate and differ in fermionic parity. We prove the uniqueness of the obtained ground states and show that they can be continuously deformed to the ground states of the non-interacting Kitaev chain without gap closing. We also demonstrate explicitly that there exists a set of operators each of which maps one of the ground states to the other with opposite fermionic parity. These operators can be thought of as an interacting generalization of Majorana edge zero modes.

We developed an Escherichia coli cell-based system to generate proteins containing 3-iodo-L-tyrosine at desired sites, and we used this system for structure determination by single-wavelength anomalous dispersion (SAD) phasing with the strong iodine signal. Tyrosyl-tRNA synthetase from Methanocaldococcus jannaschii was engineered to specifically recognize 3-iodo-L-tyrosine. The 1.7 A crystal structure of the engineered variant, iodoTyrRS-mj, bound with 3-iodo-L-tyrosine revealed the structural basis underlying the strict specificity for this nonnatural substrate; the iodine moiety makes van der Waals contacts with 5 residues at the binding pocket. E. coli cells expressing iodoTyrRS-mj and the suppressor tRNA were used to incorporate 3-iodo-L-tyrosine site specifically into the ribosomal protein N-acetyltransferase from Thermus thermophilus. The crystal structure of this enzyme with iodotyrosine was determined at 1.8 and 2.2 Angstroms resolutions by SAD phasing at CuK alpha and CrK alpha wavelengths, respectively. The native structure, determined by molecular replacement, revealed no significant structural distortion caused by iodotyrosine incorporation.

Magnetic dipole-dipole interaction dominated Bose-Einstein condensates are discussed under spinful situations. We treat the spin degrees of freedom as a classical spin vector, approaching from large spin limit to obtain an effective minimal Hamiltonian; a version extended from a non-linear sigma model. By solving the Gross-Pitaevskii equation we find several novel spin textures where the mass density and spin density are strongly coupled, depending upon trap geometries due to the long-range and anisotropic natures of the dipole-dipole interaction.PACS numbers: 03.75. Mn, 03.75.Hh, 67.57.Fg Bose-Einstein condensates (BEC) with internal degrees of freedom, the so-called spinor BEC have attract much attention experimentally and theoretically in recent years [1]. Spinor BEC opens up a new paradigm where the order parameter of condensates is described by a multi-component vector [2,3]. This can be possible by optically trapping cold atoms where all hyperfine states are liberated, while magnetic trapping freezes its freedom. So far 23 Na (the hyperfine state F = 1), and 87 Rb (F = 2) are extensively investigated.Griesmaier et al. [4] have recently succeeded in achieving BEC of 52 Cr atom gases whose magnetic moment per atom is 3 µ B (Bohr magneton). There has been already emerging [5] several novel aspects associated with larger magnetic moment in 52 Cr atom even in this magnetic trapping, where all spin moments are polarized along an external magnetic field. Namely the magnetic dipoledipole (d-d) interaction, which is proportional to F 2 is expected to play an important role in a larger spin atom.It is natural to expect realization of BEC with still larger spin atomic species under the spinful situations by optical trapping or control the d-d interaction via the Feshbach resonance relative to other interaction channels. There has already been existing a large amount of theoretical studies for dipolar BEC [6]. Most of them treat the polarized case where the dipolar moments are aligned along an external field. The intrinsic anisotropic or tensorial nature of the d-d interaction relative to the polarization axis manifests itself in various properties. The head-to-tail moment arrangement due to the d-d interaction is susceptible to a shape instability by concentrating atoms in the central region. We have seen already that tensorial and long-ranged d-d interaction is responsible for this kind of shape dependent phenomenon where the mass density is constrained by the polarization axis.In contrast the theoretical studies of the spinor dipolar BEC are scarce, and just started with several impressive works [7,8,9,10]. They consider either the F = 1 spinor BEC by taking into account the d-d interaction or F = 3 for 52 Cr atom gases in a realistic situation. Here one must handle a 7-component spinor with 5 different interaction channels g 0 , g 2 , g 4 , g 6 , and g d . The parameter space to hunt is large and difficult enough to find a stable configuration. The situation becomes further hard towards a larger F where the d-d...

Quantized vortex core structure is theoretically investigated in Fermion superfluids with population imbalance for two atom species of neutral atom clouds near a Feshbach resonance. In contrast with vortex core in balance case where the quantum depletion makes a vortex visible through the density profile measurement, the vortex core is filled in and becomes less visible because the quantized discrete bound states are occupied exclusively by the majority species. Yet it is shown that the core can be visible through the minority density profile experiment using phase contrast imaging, revealing an interesting opportunity to examine low-lying Fermionic core bound states unexplored so far.PACS numbers: 03.75. Ss,03.75.Hh, There has been much attention focused on Fermionic superfluids of cold atoms, such as 6 Li or 40 K since experimental realization [1]. The experiments utilize the Feshbach resonance by changing an external field to tune the atom-atom interaction, achieving the BEC-BCS crossover. A keen interest is now placed on Fermion superfluidity when the population of the two species (up and down "spins") is unequal experimentally [2,3,4,5] and theoretically [6,7]. Zwierlein et al. [2,3] have succeeded in creating vortices not only in the balance case with equal population, but also in the imbalance case, directly demonstrating its superfluidity. Here the presence or absence of vortices in a system is utilized to monitor superfluidity because quantized vortex is a hallmark of superfluidity. They have observed the clear signature of vortices in the inner region of the density after sweeping into the BEC side, even in the imbalance case of the BCS side. However, it is important to notice that whether the superfluidity in the outer region is robust or not is still open to question. In this Letter, we focus on the visibility of the vortex core situated at the trap center in the imbalance case. In addition, we discuss the visibility of vortices in the outer region from the results. This result is quite contrasted in the BEC case where vortices are remarkably arranged regularly throughout whole system, even near the boundary with lower density [8].The order parameter is Ψ BEC = n(r) (n(r) is the number density) in BEC, while the Cooper pair amplitude Ψ BCS ∝ c † k↑ c † −k↓ in BCS. Thus it is not self-evident even in the 50%-50% balance case that the vortex, which is probed by the density contrast, continues to be "seen" from BEC to BCS across the Feshbach resonance point. A theoretical question here is to understand the peculiar vortex core structure in the imbalance case, related to the quantum depletion of the density at the core [9, 10]. We provide a microscopic calculation for it, fully taking account of low-lying Fermionic excitations around a core beyond simple local density approximation. These individual excitations are essential in Fermion superfluid, a feature completely absent in the vortex state in Boson superfluid.This study might be useful for other research fields such as condensed matter community bec...