Compact shell solitons in K field theories

Some models providing shell-shaped static solutions with compact support (compactons) in 3+1 and 4+1 dimensions are introduced, and the corresponding exact solutions are calculated analytically. These solutions turn out to be topological solitons, and may be classified as maps $S^3 \to S^3$ and suspended Hopf maps, respectively. The Lagrangian of these models is given by a scalar field with a non-standard kinetic term (K field) coupled to a pure Skyrme term restricted to $S^2$, rised to the appropriate power to avoid the Derrick scaling argument. Further, the existence of infinitely many exact shell solitons is explained using the generalized integrability approach. Finally, similar models allowing for non-topological compactons of the ball type in 3+1 dimensions are briefly discussed.Comment: 10 pages, latex, 2 figures, change in title and introduction. Discussion section, 2 figures and references adde

New Measure of the Dissipation Region in Collisionless Magnetic Reconnection

A new measure to identify a small-scale dissipation region in collisionless magnetic reconnection is proposed. The energy transfer from the electromagnetic field to plasmas in the electron's rest frame is formulated as a Lorentz-invariant scalar quantity. The measure is tested by two-dimensional particle-in-cell simulations in typical configurations: symmetric and asymmetric reconnection, with and without the guide field. The innermost region surrounding the reconnection site is accurately located in all cases. We further discuss implications for nonideal MHD dissipation

Gauged compact Q-balls and Q-shells in a multi-component CPNCP^N model

We study a multicomponent $CP^N$ model's scalar electrodynamics. The model contains Q-balls/shells, which are non-topological compact solitons with time dependency $e^{i\omega t}$. Two coupled $CP^N$ models can decouple locally if one of their $CP^N$ fields takes the vacuum value. Because of the compacton nature of solutions, Q-shells can shelter another compact Q-ball or Q-shell within their hollow region. Even if compactons do not overlap, they can interact through the electromagnetic field. We investigate how the size of multi-compacton formations is affected by electric charge. We are interested in structures with non-zero or zero total net charge.Comment: 23 pages, 8 figure

Bertholletia excelsa Bonpl. seed removal in a primary forest in the Southwest Amazon.

Bertholletia excelsa Bonpl. (Brazil nut) is an important extractive resource and one of the main sources of income for many traditional forest communities. The agouti (Dasyprocta spp.) is primarily responsible for seed removal and dispersal as this species has its seeds enclosed in a fibrous endocarp that most species cannot penetrate. The objective of this study was to quantify the rate of Brazil nut seed removal and to photograph possible seed dispersers and predators

Pullback of the Volume Form, Integrable Models in Higher Dimensions and Exotic Textures

A procedure allowing for the construction of Lorentz invariant integrable models living in d+1 dimensional space-time and with an n dimensional target space is provided. Here, integrability is understood as the existence of the generalized zero-curvature formulation and infinitely many conserved quantities. A close relation between the Lagrange density of the integrable models and the pullback of the pertinent volume form on target space is established. Moreover, we show that the conserved currents are Noether currents generated by the volume preserving diffeomorphisms. Further, we show how such models may emerge via abelian projection of some gauge theories. Then we apply this framework to the construction of integrable models with exotic textures. Particularly, we consider integrable models providing exact suspended Hopf maps i.e., solitons with a nontrivial topological charge of pi_4(S^3). Finally, some families of integrable models with solitons of pi_n(S^n) type are constructed. Infinitely many exact solutions with arbitrary value of the topological index are found. In addition, we demonstrate that they saturate a Bogomolny bound.Comment: 23 page

Compact oscillons in the signum-Gordon model

We present explicit solutions of the signum-Gordon scalar field equation which have finite energy and are periodic in time. Such oscillons have a strictly finite size. They do not emit radiation.Comment: 12 pages, 4 figure

Regeneration of Carapa guianensis (Aublet.) seedings in two forest types in Rio Branco, Acre, Brazil.

Extractive use of Carapa guianensis (andiroba), a multi-use species, provides an alternative for sustainable resource use. The objective of this study was to investigate the mortality of seedlings and saplings of Carapa guianensis, comparing two forest types (upland and occasionally inundated forest) at Embrapa’s experimental forest reserve in Acre, Brazil

Scaling and a Fokker-Planck model for fluctuations in geomagnetic indices and comparison with solar wind as seen by Wind and ACE

The evolution of magnetospheric indices on temporal scales shorter than that of substorms is characterized by bursty, intermittent events that may arise from turbulence intrinsic to the magnetosphere or that may reflect solar wind-magnetosphere coupling. This leads to a generic problem of distinguishing between the features of the system and those of the driver. We quantify scaling properties of short-term (up to few hours) fluctuations in the geomagnetic indices AL and AU during solar minimum and maximum, along with the parameter that is a measure of the solar wind driver. We find that self-similar statistics provide a good approximation for the observed scaling properties of fluctuations in the geomagnetic indices, regardless of the solar activity level, and in the parameter at solar maximum. This self-similarity persists for fluctuations on timescales at least up to about 1–2 hours. The scaling exponent of AU index fluctuations show dependence on the solar cycle, and the trend follows that found in the scaling of fluctuations in . The values of their corresponding scaling exponents, however, are always distinct. Fluctuations in the AL index are insensitive to the solar cycle, as well as being distinct from those in the parameter. This approximate self-similar scaling leads to a Fokker-Planck model which, we show, captures the probability density function of fluctuations and provides a stochastic dynamical equation (Langevin equation) for time series of the geomagnetic indices

Comparing seed production and regeneration of Carapa guianensis (Aublet.) in two forest types in Acre, Brazil from 2004 to 2007.

Carapa guianensis is a tropical tree valuable for its seed oil and timber. This study compared Carapa seed production and regeneration density in two forest types: upland and occasionally inundated