3,128 research outputs found
Composite Skyrme Model with Vector Mesons
We study the composite Skyrme model, proposed by Cheung and G\"{u}rsey,
introducing vector mesons in a chiral Lagrangian. We calculate the static
properties of baryons and compare with results obtained from models without
vector mesons.Comment: LaTeX, 9 pages, 3 figures, to be published in Phys. Rev.
The "recoil" correction of order to hyperfine splitting of positronium ground state
The "recoil" correction of order to the hyperfine splitting of
positronium ground state was found. The formalism employed is based on the
noncovariant perturbation theory in QED. Equation for two-particle component of
full (many-body) wave function is used, in which effective Hamiltonian depends
on the energy of a system. The effective Hamiltonian is not restricted to the
nonrelativistic region, so there is no need in any regularization. To evaluate
integrals over loop momenta, they are divided into "hard" and "soft" parts,
coming from large and small momenta respectively. Soft contributions were found
analytically, and hard ones are evaluated by numerical integration. Some soft
terms due to the retardation cancel each other. To calculate the "hard"
contributions, a great number of noncovariant graphs is replaced by only a few
covariant ones. The hard contribution was found in two ways. The first way is
to evaluate contributions of separate graphs, using the Coulomb gauge. The
second one is to calculate full hard contribution as a whole using the Feynman
gauge. The final result for the "recoil" correction is 0.381(6) m\al^6 and
agrees with those of previous papers. Diagram-to-diagram comparison with the
revised results of Adkins&Sapirstein was done. All the results agree, so the
"recoil" correction is now firmly established. This means a considerable
disagreement with the experimental data.Comment: 28 pages, latex including latex figure
Remarks on the Collective Quantization of the SU(2) Skyrme Model
We point out the question of ordering momentum operator in the canonical
\break quantization of the SU(2) Skyrme Model. Thus, we suggest a new
definition for the momentum operator that may solve the infrared problem that
appears when we try to minimize the Quantum Hamiltonian.Comment: 8 pages, plain tex, IF/UFRJ/9
Radiocarbon dating of deep-sea corals
Deep-sea corals are a promising new archive of paleoclimate. Coupled radiocarbon and U-series dates allow ^(14)C to be used as a tracer of ocean circulation rate in the same manner as it is used in the modern ocean. Diagnetic alteration of coral skeletons on the seafloor requires a thorough cleaning of contaminating phases of carbon. In addition, 10% of the coral must be chemically leached prior to dissolution to remove adsorbed modern CO_2. A survey of modern samples from the full Δ^(14)C gradient in the deep ocean demonstrates that the coralline CaCO_3 records the radiocarbon value of the dissolved inorganic carbon
Pricing Bodies: A Feminist New Materialist Approach to the Relations Between the Economic and Socio-Cultural
Arguments that the economic and socio-cultural should be understood as relational and intertwined, and that price involves a reciprocal relationship between the economic and socio-cultural, are increasingly prevalent in the social sciences. I develop these notions of relationality and reciprocation through a feminist new materialist perspective, which emphasises the entanglement of and intra-action between what might usually be seen as independent and autonomous entities. To do this, I focus on a range of recent body-image initiatives, led by government, corporate and non-profit organisations, which aim to improve girls’ and young women’s levels of confidence and self-esteem. I explore how feminist theory tends to see such initiatives in terms of the expansion of the economic sphere into the socio-cultural, which involves a tainting or contamination of embodiment and feeling. Rather than dispute these arguments, I take seriously theories and practices from cultural economy that see the economic and socio-cultural as co-constitutive. I augment these ideas with a feminist new materialist approach and argue that the economic and socio-cultural are in intra-active relations: they do not precede or exist apart from each other. In doing so, I consider how body-image initiatives can be understood as phenomena produced through these entangled intra-active relations, and offer an understanding of pricing as a simultaneously socio-cultural and economic process, where value and values become. I also raise questions regarding how, ethically and politically, boundary making and unmaking can be conceived, and how despite being in entangled relations, asymmetries between economic and socio-cultural relations may be approached
Positronium S state spectrum: analytic results at O(m alpha^6)
We present an analytic calculation of the O(m alpha^6) recoil and radiative
recoil corrections to energy levels of positronium nS states and their
hyperfine splitting. A complete analytic formula valid to O(m alpha^6) is given
for the spectrum of S states. Technical aspects of the calculation are
discussed in detail. Theoretical predictions are given for various energy
intervals and compared with experimental results.Comment: 29 pages, revte
SU(2) Skyrme Vortices
A regular method for constructing vortex-like solutions with cylindrical
symmetry to the equations of the SU(2) Skyrme chiral model is proposed. A
numerical estimate for the length density of mass is given
Skyrmions and domain walls in (2+1) dimensions
We study classical solutions of the vector O(3) sigma model in (2+1)
dimensions, spontaneously broken to O(2)xZ2. The model possesses Skyrmion-type
solutions as well as stable domain walls which connect different vacua. We show
that different types of waves can propagate on the wall, including waves
carrying a topological charge. The domain wall can also absorb Skyrmions and,
under appropriate initial conditions, it is possible to emit a Skyrmion from
the wall.Comment: plain tex : 15 pages, 21 Postscript figures, uses epsf.te
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