AbstractThe Fermi surface depletion of beta-stable nuclear matter is calculated to study its effects on several physical properties that determine the neutron star (NS) thermal evolution. The neutron and proton Z factors measuring the corresponding Fermi surface depletions are calculated within the Brueckner-Hartree-Fock approach, employing the AV18 two-body force supplemented by a microscopic three-body force. Neutrino emissivity, heat capacity, and in particular neutron (PF2)-P-3 superfluidity, turn out to be reduced, especially at high baryonic density, to such an extent that the cooling rates of young NSs are significantly slowed. DOI:10.3847/0004-637X/817/1/6 https://arxiv.org/pdf/1512.02746.pdf
“The first trillionaire will be made in space,” US Republican Senator Ted Cruz told scientists and entrepreneurs in May at a Washington DC summit on sending humans to Mars. He could be right, but only if we rethink space technology.The cost of launching a satellite is comparable with the value of its weight in gold. It takes thousands of dollars to send one kilogram into low Earth orbit, often ten times more than that. Returning material is even more expensive: it cost the equivalent of US$250 billion per kilogram of sample for Japan’s Hayabusa spacecraft to bring back less than 1 gram of asteroid grains in 2010. The price tag for the whole mission was $250 million.Still, space is big business. Globally, companies invested about $262 billion in 2016, mostly on using satellites for telecommunications, navigation and remote sensing1 (see ‘Lift-off’). Governments, too, spend billions — about $84 billion worldwide in 2016. More than half that ($48 billion) was from the United States, mainly for military, meteorological and communications purposes.Nature 562, 185-187 (2018)DOI: 10.1038/d41586-018-06957-2https://www.nature.com/articles/d41586-018-06957-2
AbstractExtreme-mass-ratio inspirals (EMRIs) are important gravitational-wave (GW) sources for future space-based detectors. The standard model consists of one stellar-mass black hole spiraling into a supermassive one, and such a process emits low-frequency (~10−3 Hz) GWs, which contain rich information about the space–time geometry around the central massive body. Here we show that the small bodies in EMRIs, in fact, could be binary black holes, which are captured by the massive black holes during earlier close encounters. About 30% of the captured binaries coalesce due to the perturbation by the massive bodies, resulting in a merger rate of 0.03 Gpc3 yr−1 in the most optimistic scenario. The coalescence generates also high-frequency (~102 Hz) GWs detectable by ground-based observatories, making these binary-EMRIs ideal targets for future multi-band GW observations. DOI: 10.1038/s42005-018-0053-0 https://sci-hub.tw/10.1038/s42005-018-0053-0
AbstractThe observations combined with theory of neutron star (NS) cooling play a crucial role in achieving the intriguing information of the stellar interior, such as the equation of state (EOS), composition and superfluidity of dense matter. The traditional NS cooling theory is based on the assumption that the stellar structure does not change with time. The validity of such a static description has not yet been confirmed. We generalize the theory to a dynamic treatment; that is, continuous change of the NS structure (rearrangement of the stellar density distribution with the total baryon number fixed) as the decrease of temperature during the thermal evolution, is taken into account. It is found that the practical thermal energy used for the cooling is slightly lower than that is estimated in static situation, and hence the cooling of NSs is accelerated correspondingly but the effect is rather weak. Therefore, the static treatment is a good approximation in the calculations of NS cooling. https://iopscience.iop.org/article/10.3847/1538-4357/aacc60
AbstractIn this paper, I present the recently established hyperunified field theory (HUFT) for all basic forces and elementary particles within the framework of gravitational quantum field theory (GQFT) in hyper-space–time. GQFT treats gravity as a gauge theory in the framework of quantum field theory to avoid the long term obstacle between general relativity and quantum mechanics. HUFT is built based on the guiding principle: the dimension of hyper-space–time correlates to intrinsic quantum numbers of basic building blocks of nature, and the action describing the laws of nature obeys the gauge invariance and coordinate independence, which is more fundamental than that proposed by Einstein for general relativity. The basic gravitational field is defined in biframe hyper-space–time as a bicovariant vector field, it is a gauge-type hyper-gravifield rather than a metric field. HUFT is characterized by a bimaximal Poincaré and hyper-spin gauge symmetry PO(1,Dh−1)⨝SP(1,Dh−1) with a global and local conformal scaling invariance in biframe hyper-space–time. The gravitational origin of gauge symmetry is revealed through the hyper-gravifield that plays an essential role as a Goldstone-like field, which enables us to demonstrate the gauge-gravity and gravity-geometry correspondences and to corroborate the gravitational gauge-geometry duality with an emergent hidden general linear group symmetry GL(Dh,R). The Taiji Program in Space for the gravitational wave detection in China is briefly outlined.DOI: 10.1142/S0217751X18440141https://www.worldscientific.com/doi/abs/10.1142/S0217751X18440141
AbstractWe present a three-dimensional modeling of the Milky Way dust distribution by fitting the value-added star catalog of the LAMOST spectral survey. The global dust distribution can be described by an exponential disk with a scale length of 3192 pc and a scale height of 103 pc. In this modeling, the Sun is located above the dust disk with a vertical distance of 23 pc. Besides the global smooth structure, two substructures around the solar position are also identified. The one located at 150° < l < 200° and -5° < b < -30° is consistent with the Gould Belt model of Gontcharov, and the other one located at 140° < l < 165° and 0° < b < 15° is associated with the Camelopardalis molecular clouds. DOI: 10.3847/1538-4357/aabaefhttps://iopscience.iop.org/article/10.3847/1538-4357/aabaef/pdf
AbstractWe report the observation of a controlled Landau-Zener transition (LZT) in Rydberg atoms by breaking the symmetry of the underlying Hamiltonian. For a nonhydrogenic Rydberg atom inside a changing electric (F) field, a LZT occurs between the avoided crossing energy levels of neighboring Rydberg states only for a sufficiently high changing rate. If a transverse magnetic (B) field is applied as we implement, the atomic level symmetry is broken, which causes the Stark manifolds denoted by a different |m| (m is the magnetic quantum number) to interact with each other. The mixed state levels end up pushing the adiabatically repelled target states closer and additionally they serve as stepping stones for the sequential LZTs between the neighboring sublevels. Such a feature significantly decreases the changing rate required for an efficient LZT inside a pure electric field. We report experimental observations that support the above scenario. It opens a versatile approach for engineering a controlled LZT in more general systems. DOI: 10.1103/PhysRevLett.120.063203https://pubmed.ncbi.nlm.nih.gov/29481261/Supported by the National Key Basic Research and Development Program and the National Natural Science Foundation of China.
AbstractDue to the development of ground-based, large-aperture solar telescopes with adaptive optics (AO) resulting in increasing resolving ability, more accurate sunspot identifications and characterizations are required. In this article, we have developed a set of automated segmentation methods for high-resolution solar photospheric images. Firstly, a local-intensity-clustering level-set method is applied to roughly separate solar granulation and sunspots. Then reinitialization-free level-set evolution is adopted to adjust the boundaries of the photospheric patch; an adaptive intensity threshold is used to discriminate between umbra and penumbra; light bridges are selected according to their regional properties from candidates produced by morphological operations. The proposed method is applied to the solar high-resolution TiO 705.7-nm images taken by the 151-element AO system and Ground-Layer Adaptive Optics prototype system at the 1-m New Vacuum Solar Telescope of the Yunnan Observatory. Experimental results show that the method achieves satisfactory robustness and efficiency with low computational cost on high-resolution images. The method could also be applied to full-disk images, and the calculated sunspot areas correlate well with the data given by the National Oceanic and Atmospheric Administration (NOAA). DOI: 10.1007/s11207-017-1236-7 https://link.springer.com/article/10.1007%2Fs11207-017-1236-7
AbstractA hyperunified field theory is built in detail based on the postulates of gauge invariance and coordinate independence along with the conformal scaling symmetry. All elementary particles are merged into a single hyper-spinor field and all basic forces are unified into a fundamental interaction governed by the hyper-spin gauge symmetry SP(1, Dh−1). The dimension Dh of hyper-spacetime is conjectured to have a physical origin in correlation with the hyper-spin charge of elementary particles. The hyper-gravifield fiber bundle structure of biframe hyper-spacetime appears naturally with the globally flat Minkowski hyper-spacetime as a base spacetime and the locally flat hyper-gravifield spacetime as a fiber that is viewed as a dynamically emerged hyper-spacetime characterized by a non-commutative geometry. The gravitational origin of gauge symmetry is revealed with the hyper-gravifield that plays an essential role as a Goldstone-like field. The gauge–gravity and gravity–geometry correspondences bring about the gravitational gauge–geometry duality. The basic properties of hyperunified field theory and the issue on the fundamental scale are analyzed within the framework of quantum field theory, which allows us to describe the laws of nature in deriving the gauge gravitational equation with the conserved current and the geometric gravitational equations of Einstein-like type and beyond.DOI: 10.1140/epjc/s10052-017-5504-3https://link.springer.com/article/10.1140/epjc/s10052-017-5504-3Supported by the Chinese Academy of Sciences' Strategic Leading Science and Technology Project, Frontier Science Key Research Program, and the National Natural Science Foundation of China.
AbstractWe demonstrate high fidelity single-qubit gate operation in a trapped single neutral atom. The atom is trapped in the recently invented magic-intensity optical dipole trap (MI-ODT) with more stable magnetic field. The MI-ODT efficiently mitigates the detrimental effects of light shifts thus sufficiently improves the performance of single qubit-gates. The gates are driven with microwave, and the fidelity of gate operation is characterized by using the randomized benchmarking method. We obtain an average error per Clifford gate of 3.0（7）∗10-5 which is much below the error threshold (10-4) for fault-tolerance. This error is found to be dominated by qubit dephasing, and the corresponding coherence time relevant to the Clifford gates is also measured experimentally. This work is an essential step toward the construction of a scalable quantum computer with neutral atoms trapped in an MI-ODT array. DOI: 10.1103/PhysRevLett.121.240501 http://export.arxiv.org/pdf/1712.06306
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