454 research outputs found
Impact of satellite gravity missions on glaciology and Antarctic Earth sciences
Satellite gravity missions in the 21st Century are expected to be beneficial to multi-disciplinary scientific objectives. Especially, the Gravity Recovery And Climate Experiment (GRACE) and its follow-on missions will provide not only data for precise gravity mapping but also time series of global gravity field coefficients at intervals of about 15 days to two months. These data are precise enough to reveal the temporal variations of the gravity fields due to mass redistribution in and on the Earth. From the viewpoint of Earth sciences in the Antarctic region, the data are expected to contribute to studies of ice sheet mass balance and postglacial rebound as well as other geodetic and geophysical problems. These issues have been mainly investigated based on the degree variance analyses of the gravity field so far. In this paper, we briefly review the gravity mission data from the viewpoint of along track geoid height variations which are more direct results of the mass variations, and then discuss some of the issues related to in-situ observations
Hadron-Hadron Interactions from Imaginary-time Nambu-Bethe-Salpeter Wave Function on the Lattice
Imaginary-time Nambu-Bethe-Salpeter (NBS) wave function is introduced to
extend our previous approach for hadron-hadron interactions on the lattice.
Scattering states of hadrons with different energies encoded in the NBS
wave-function are utilized to extract non-local hadron-hadron potential. "The
ground state saturation", which is commonly used in lattice QCD but is hard to
be achieved for multi-baryons, is not required. We demonstrate that the present
method works efficiently for the nucleon-nucleon interaction (the potential and
the phase shift) in the 1S_0 channel.Comment: 13 pages, 6 figure
Baryon-Baryon Interactions in the Flavor SU(3) Limit from Full QCD Simulations on the Lattice
We investigate baryon-baryon (BB) interactions in the 3-flavor full QCD
simulations with degenerate quark masses for all flavors. The BB potentials in
the orbital S-wave are extracted from the Nambu-Bethe-Salpeter wave functions
measured on the lattice. We observe strong flavor-spin dependences of the BB
potentials at short distances. In particular, a strong repulsive core exists in
the flavor-octet and spin-singlet channel (the 8_s representation), while an
attractive core appears in the flavor singlet channel (the 1 representation).
We discuss a relation of such flavor-spin dependence with the Pauli exclusion
principle in the quark level. Possible existence of an H-dibaryon resonance
above the Lambda-Lambda threshold is also discussed.Comment: 16 pages, 4 figures, ptptex.cls use
interaction from 2+1 flavor lattice QCD
We investigate the interaction between baryons in the
channel from 2+1 flavor lattice QCD simulations. On the basis of the HAL QCD
method, the potential is extracted from the Nambu-Bethe-Salpeter
wave function calculated on the lattice by using the PACS-CS gauge
configurations with the lattice spacing fm, the lattice volume
fm and the quark masses corresponding to MeV
and MeV. The potential has a repulsive
core at short distance and an attractive well at intermediate distance.
Accordingly, the phase shift obtained from the potential shows moderate
attraction at low energies. Our data indicate that the system
with the present quark masses may appear close to the unitary limit where the
scattering length diverges.Comment: 9 pages, 4 figures, 1 tabl
Are two nucleons bound in lattice QCD for heavy quark masses? -- Consistency check with L\"uscher's finite volume formula --
On the basis of the L\"uscher's finite volume formula, a simple test
(consistency check or sanity check) is introduced and applied to inspect the
recent claims of the existence of the nucleon-nucleon () bound state(s) for
heavy quark masses in lattice QCD. We show that the consistency between the
scattering phase shifts at and/or obtained from the lattice
data and the behavior of phase shifts from the effective range expansion (ERE)
around exposes the validity of the original lattice data, otherwise
such information is hidden in the energy shift of the two nucleons
on the lattice. We carry out this sanity check for all the lattice results in
the literature claiming the existence of the bound state(s) for heavy
quark masses, and find that (i) some of the data show clear inconsistency
between the behavior of ERE at and that at , (ii) some of
the data exhibit singular behavior of the low energy parameter (such as
the divergent effective range) at , (iii) some of the data have the
unphysical residue for the bound state pole in S-matrix, and (iv) the rest of
the data are inconsistent among themselves. Furthermore, we raise a
caution of using the ERE in the case of the multiple bound states. Our finding,
together with the fake plateau problem previously pointed out by the present
authors, brings a serious doubt on the existence of the bound states for
pion masses heavier than 300 MeV in the previous studies.Comment: 39 pages, 16 figures, and 11 tables, title changed, references and
comment adde
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