AbstractWe derive the generalized partial wave expansion for M → N scattering amplitude in terms of spinor helicity variables. The basis amplitudes of the expansion with definite angular momentum j consist of the Poincare Clebsch-Gordan coefficients, while j constrains the UV physics that could generate the corresponding operators at tree level. Moreover, we obtain a series of selection rules that restrict the anomalous dimension matrix of effective operators and the way how effective operators contribute to some 2 → N amplitudes at the loop level.https://arxiv.org/pdf/2001.04481.pdf
AbstractOrbital angular momentum (OAM) of light represents a fundamental optical freedom that can be exploited to manipulate quantum state of atoms. In particular, it can be used to realize spin-orbital-angular-momentum (SOAM) coupling in cold atoms by inducing an atomic Raman transition using two laser beams with differing OAM. Rich quantum phases are predicted to exist in many-body systems with SOAM coupling. Their observations in laboratory, however, are often hampered by the limited control of the system parameters. In this work we report, for the first time, the experimental observation of the ground-state quantum phase diagram of the SOAM coupled Bose-Einstein condensate (BEC). The discontinuous variation of the spin polarization as well as the vorticity of the atomic wave function across the phase boundaries provides clear evidence of first-order phase transitions. Our results open up a new way to the study of phase transitions and exotic quantum phases in quantum gases.DOI: 10.1103/physrevlett.122.110402 https://journals.aps.org/prl/pdf/10.1103/PhysRevLett.122.110402
Abstract Practically all solar phenomena are more or less relative to the solar magnetic field. It produces relatively stable structures like sunspots or prominences and is responsible for spectacular dynamic phenomena like flares or coronal mass ejections. However, the generation, amplification and destruction of magnetic fields remain poorly understood. The knowledge of its magnitude and direction is crucial for interpreting measurements of other parameters, and it can be measured usually by a polarimetry at some special spectral lines, which should be sensitive to the Zeeman effect. To answer what physical mechanisms are responsible for heating the corona, what causes variations of radiative output in the Sun, and what mechanisms trigger flares and coronal mass ejections and so on, many large aperture solar telescope have been developed (such as VTT, GREGOR, NST) or have being developed (such as DKIST, EST), and the Stokes polarimetry is their most important observational device for determining the magnetic field. The Chinese large solar telescope (CLST) with a 1.8-m aperture is a classic Gregorian configuration telescope with an alt-azimuth mount. It will be the second largest solar telescope in the world for a long time. And it is the main task for the Chinese large solar telescope (CLST) to measure the solar polarization with a high accuracy and sensitivity. However, as a classic Gregorian configuration telescope with an alt-azimuth mount, the telescope system itself will introduce instrumental polarization. And it also will change constantly with the rotating of the telescope. Therefore a calibration unit which produces light of known polarization states is necessary to measure the Muller matrix of the system and apply the correction numerically on the measured Stokes vector.DOI: 10.12086/oee.2018.180058http://www.oejournal.org/J/OEE/Article/Details/A181101000003/CNSupported by National Natural Science Foundation of China (11178004, 11727805)
AbstractAn emergent global symmetry of the composite sector (called maximal symmetry) can soften the ultraviolet behavior of the Higgs potential and also significantly modify its structure. We explain the conditions for the emergence of maximal symmetry as well as its main consequences. We present two simple implementations and generalize both to N-site as well as full warped extra dimensional models. The gauge symmetry of these models enforces the emergence of maximal symmetry. The corresponding Higgs potentials have unique properties: one case minimizes the tuning while the other allows heavy top partners evading direct LHC bounds.DOI:10.1103/PhysRevLett.124.241801https://arxiv.org/pdf/1810.07704.pdf
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