Maxwellian Term Research Articles

Constraining anisotropic models of the early universe with WMAP9 data

We constrain several models of the early Universe that predict a statistical anisotropy of the cosmic microwave background (CMB) sky. We make use of WMAP9 maps deconvolved with beam asymmetries. As compared to previous releases of WMAP data, they do not exhibit the anomalously large quadrupole of statistical anisotropy. This allows to strengthen the limits on the parameters of models established earlier in the literature. In particular, the amplitude of the special quadrupole is constrained as |g_*|<0.072 at 95% C.L. (-0.046<g_*<0.048 at 68% C.L.) independently of the preferred direction in the sky. The upper limit is obtained on the total number of e-folds in anisotropic inflation with the Maxwellian term nonminimally coupled to the inflaton, namely N_{tot} <N_{CMB} +82 at 95% C.L. (+14 at 68% C.L.) for N_{CMB}=60. We also constrain models of the (pseudo)conformal universe. The strongest constraint is obtained for spectator scenarios involving a long stage of subhorizon evolution after conformal rolling, which reads h^2 < 0.006 at 95% C.L., in terms of the relevant parameter. The analogous constraint is much weaker in dynamical models, e.g., Galilean genesis.

Regular cosmological bouncing solutions in low energy effective action from string theories

The possibility of obtaining singularity free cosmological solutions in four dimensional effective actions motivated by string theory is investigated. In these effective actions, in addition to the Einstein-Hilbert term, the dilatonic and the axionic fields are also considered as well as terms coming from the Ramond-Ramond sector. A radiation fluid is coupled to the field equations, which appears as a consequence of the Maxwellian terms in the Ramond-Ramond sector. Singularity free bouncing solutions in which the dilaton is finite and strictly positive are obtained for models with flat or negative curvature spatial sections when the dilatonic coupling constant is such that $\omega < - 3/2$, which may appear in the so called $F$ theory in 12 dimensions. These bouncing phases are smoothly connected to the radiation dominated expansion phase of the standard cosmological model, and the asymptotic pasts correspond to very large flat spacetimes.

Gauging of 1d-space translations for nonrelativistic point particles

Gauging of space translations for nonrelativistic point particles in one dimension leads to general coordinate transformations with fixed Newtonian time. The minimal gauge invariant extension of the particle velocity requires the introduction of two gauge fields whose minimal self interaction leads to a Maxwellian term in the Lagrangian. No dilaton field is introduced. We fix the gauge such that the residual symmetry group is the Galilei group. In case of a line the two-particle reduced Lagrangian describes the motion in a Newtonian gravitational potential with strength proportional to the energy. For particles on a circle with certain initial conditions we only have a collective rotation with constant angular velocity.

Sunspot's electromagnetism with a locally gauge-invariant chern-simons term

We present a (2+1)-dimensional sunspot model whose Lagrange density contains, in addition to the classical Maxwellian term, the so-called Chern-Simons term generalized here in a gauge-invariant way. It is shown that it is namely this term which is responsible for the confinement of the spot's electromagnetic field into a finite-dimensional domain. We further demonstrate that besides the total magnetic flux it is also the spot's electric charge which is non-zero and that both quantities are topologically quantized, i.e. can acquire discrete values only. Finally, a cylindrically symmetric sunspot carryingp magnetic flux quanta,p being a positive integer, is revealed to possess a non-zero total angular momentum, the magnitude of which is proportional top2. The latter fact also implies the stability of rotating sunspots against their fragmentation (splitting).

The stress relaxation of the 1,2‐syndiotactic polybutadiene thermoplastic elastomer

Abstract The stress relaxation of a low‐crystallinity type thermoplastic elastomer (TPR), 1,2‐syndiotactic polybutadiene, was studied. By using the continuous and intermittent stress relaxation method, the Co60 r‐ray irradiated samples were tested from 30°C to 106°C under air, nitrogen or oxygen atmosphere. The relative stress relaxation curve of this low crystallinity kind of elastomer can be expressed by two Maxwellian decay terms. f(t)/f(0)=o 1 exp (‐k 1 t) + o 2 exp (‐k 2 t) Since there are only a few C=C double bonds in the polymer main chain, the oxidation of C=C in the side chain does not influence the strength of the stress relaxation. Thus the chemical relaxation can be ignored in this kind of thermoplastic elastomer. These two Maxwellian terms are both of physical stress relaxation, namely, flexible chain slippage and crystalline domain disintegration (breaking), respectively:

The Solution of the Boltzmann Equation for a Shock Wave

It is pointed out that the distribution of molecular velocities in a strong shock wave in a gas is bimodal. Assuming the distribution function to consist of a sum of two maxwellian terms with temperatures and mean velocities corresponding to the subsonic and supersonic streams, it is found that the space distribution, as determined by the solution of a transport equation, is appropriate to describe a shock wave. Comparison of the solutions of two different transport equations shows that the assumed distribution changes relatively slowly with time and so is an approximate stationary solution of the Boltzmann equation for strong shocks. The shock thickness found is considerably greater than that given by previous theories. The nominal thermal conduction coefficient is negative in the after part of the shock.