4,842 research outputs found
Symmetry group at future null infinity I: Scalar theory
We reduce the massless scalar field theory in Minkowski spacetime to future
null infinity. We compute the Poincar\'e flux operators, which can be
generalized and identified as the supertranslation and superrotation
generators. These generators are shown to form a closed symmetry algebra with a
divergent central charge. In the classical limit, we argue that the algebra may
be interpreted as the geometric symmetry of a Carrollian manifold, i.e., the
hypersurface of future null infinity. Our method may be used to find more
physically interesting Carrollian field theories.Comment: 51 pages, revised versio
Symmetry group at future null infinity III: Gravitational theory
We reduce the gravitational theory in an asymptotically flat spacetime to
future null infinity. We compute the Poincar\'e flux operators at future null
infinity and construct the supertranslation and superrotation generators. The
generators are shown to form a closed symmetry algebra by including a
generalized gravitational duality operator. We could regard all the generators
as the Hamiltonians with respect to the symmetry transformation in the boundary
field theory. Our construction of the generators may relate to the BMS fluxes
defined in the literature by adding counterterms to the Bondi mass and angular
momentum aspects.Comment: 67 pages, revised versio
Combined explanations of -physics anomalies, and neutrino masses by scalar leptoquarks
We extend the contents of the standard model (SM) by introducing TeV-scale
scalar leptoquarks to generate neutrino masses and explain some current
observed deviations from the SM predictions, including the anomalous magnetic
moments of charged leptons (electron and muon) and -physics anomalies
( and ). The model consists of
singlet leptoquark , doublet leptoquark
and triplet leptoquark . We combine the constraints arising from the low-energy lepton flavor
violation, meson decay and mixing observables. We perform a detailed
phenomenological analysis and identify the minimized texture of leptoquark
Yukawa matrices to accommodate a unified explanation of the anomalies and
neutrino oscillation data.Comment: 30 pages, 5 figures, matches published versio
Anomalous orbital expansion of low-mass X-ray binary 2A 1822-371: the existence of a circumbinary disk?
The source 2A 1822-371 is an eclipsing low-mass X-ray binary (LMXB)
consisting of a neutron star (NS) and a donor star in an
orbit of 5.57 hr. Based on timing of the eclipse arrival times, this source was
found to be experiencing a rapid orbital expansion with an orbital-period
derivative as ,
implying that the mass-transfer rate should be higher than at least three times
the Eddington accretion rate. The standard magnetic braking (MB) model cannot
produce such a high mass-transfer rate. The modified MB model derived by Van \&
Ivanova (2019) can produce a high mass-transfer rate, resulting in a high
. This work proposes an alternative model to account for the
anomalously high mass-transfer rate and of 2A 1822-371.
During the mass transfer, a tiny fraction of the transferred material is
thought to form a circumbinary (CB) disk around the LMXB, which can efficiently
extract orbital angular momentum from the system by the interaction between the
CB disk and the binary. We use the MESA code to model the formation and
evolution of 2A 1822-371 for different CB-disk masses. When the CB-disk mass is
, the simulation can reproduce the observed
donor-star mass, orbital period, and orbital-period derivative. Such a CB disk
can accelerate the evolution of the binary and produce a high mass transfer
rate of , driving the binary to evolve
toward a wide-orbit system. Therefore, we propose that CB disks may be
responsible for the rapid orbital changes observed in some LMXBs.Comment: 8 pages, 8 figures, Astronomy and Astrophysics in pres
Quantum flux operators in higher spin theories
We construct Carrollian higher spin field theories by reducing the bosonic
Fronsdal theories in flat spacetime to future null infinity. We extend the
Poincar\'e fluxes to quantum flux operators which generate Carrollian
diffeomorphism, namely supertranslation and superrotation. These flux operators
form a closed symmetry algebra once including a helicity flux operator which
follows from higher spin super-duality transformation. The super-duality
transformation is an angle-dependent transformation at future null infinity
which generalizes the usual electro-magnetic duality transformation. The
results agree with the lower spin cases when restricting to .Comment: 48 pages, 2 figure
Bis(2,2′-bipyridine-κ2 N,N′)(3,5-dinitro-2-oxidobenzoato-κ2 O 1,O 2)cobalt(II)
In the title compound, [Co(C7H2N2O7)(C10H8N2)2], the CoII atom is coordinated by four N atoms from two 2,2′-bipyridine ligands and two O atoms from a 3,5-dinitro-2-oxidobenzoate ligand, displaying a distorted octaÂhedral coordination geometry. The crystal structure involves C—H⋯O hydrogen bonds between the 2,2′-bipyridine ligands and the carboxylÂate and NO2 groups of the 3,5-dinitro-2-oxidobenzoate ligand
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