Vector field theories in cosmology

Recently proposed theories based on the cosmic presence of a vectorial field are compared and contrasted. In particular the so called Einstein aether theory is discussed in parallel with a recent proposal of a strained space-time theory (Cosmic Defect theory). We show that the latter fits reasonably well the cosmic observed data with only one, or at most two, adjustable parameters, whilst other vector theories use much more. The Newtonian limits are also compared. Finally we show that the CD theory may be considered as a special case of the aether theories, corresponding to a more compact and consistent paradigm.Comment: 19 pages, 1 figure, to appear on Phys. Rev.

Adiabatic population transfer via multiple intermediate states

This paper discusses a generalization of stimulated Raman adiabatic passage (STIRAP) in which the single intermediate state is replaced by $N$ intermediate states. Each of these states is connected to the initial state \state{i} with a coupling proportional to the pump pulse and to the final state \state{f} with a coupling proportional to the Stokes pulse, thus forming a parallel multi-$\Lambda$ system. It is shown that the dark (trapped) state exists only when the ratio between each pump coupling and the respective Stokes coupling is the same for all intermediate states. We derive the conditions for existence of a more general adiabatic-transfer state which includes transient contributions from the intermediate states but still transfers the population from state \state{i} to state \state{f} in the adiabatic limit. We present various numerical examples for success and failure of multi-$\Lambda$ STIRAP which illustrate the analytic predictions. Our results suggest that in the general case of arbitrary couplings, it is most appropriate to tune the pump and Stokes lasers either just below or just above all intermediate states.Comment: 14 pages, two-column revtex style, 10 figure

Counterintuitive transitions in the multistate Landau-Zener problem with linear level crossings

We generalize the Brundobler-Elser hypothesis in the multistate Landau-Zener problem to the case when instead of a state with the highest slope of the diabatic energy level there is a band of states with an arbitrary number of parallel levels having the same slope. We argue that the probabilities of counterintuitive transitions among such states are exactly zero.Comment: 9 pages, 5 figure

Post-Newtonian expansion for Gauss-Bonnet Gravity

The Parametrized Post-Newtonian expansion of gravitational theories with a scalar field coupled to the Gauss-Bonnet invariant is performed and confrontation of such theories with Solar system experiments is discussed.Comment: 4 pages; typos corrected, published versio

Adiabatic creation of coherent superposition states via multiple intermediate states

We consider an adiabatic population transfer process that resembles the well established stimulated Raman adiabatic passage (STIRAP). In our system, the states have nonzero angular momentums $J$, therefore, the coupling laser fields induce transitions among the magnetic sublevels of the states. In particular, we discuss the possibility of creating coherent superposition states in a system with coupling pattern $J=0\Leftrightarrow J=1$ and $J=1\Leftrightarrow J=2$. Initially, the system is in the J=0 state. We show that by two delayed, overlapping laser pulses it is possible to create any final superposition state of the magnetic sublevels $|2,-2>$, $|2,0>$, $|2,+2>$. Moreover, we find that the relative phases of the applied pulses influence not only the phases of the final superposition state but the probability amplitudes as well. We show that if we fix the shape and the time-delay between the pulses, the final state space can be entirely covered by varying the polarizations and relative phases of the two pulses. Performing numerical simulations we find that our transfer process is nearly adiabatic for the whole parameter set.Comment: 7 pages, 10 figure

A Taxonomy of Disgust in Art

Disgust has been a perennial feature of art from medieval visions of hell to postmodern travesties. The purpose of this chapter is to chart various ways in which disgust functions in artworks both in terms of content and style, canvassing cases in which the content and/or style is literally disgusting in contrast to cases where the disgust serves to characterize the content, often for moral or political or broader cultural purposes

Free Energy of an SU(2) Model of (2+1)-dimensional QCD in the Constant Condensate Background

Gluon and quark contributions to the thermodynamic potential (free energy) of a (2+1)-dimensional QCD model at finite temperature in the background of a constant homogeneous chromomagnetic field H combined with A_0 condensate are calculated. The role of the tachyonic mode in the gluon energy spectrum is discussed. A possibility of the free energy global minimum generation at nonzero values of H and A_0 condensates is investigated.Comment: LaTeX 2e, 14 pages, 6 eps figures, some miscalculations were correcte

B fields in OB stars (BOB): The discovery of a magnetic field in a multiple system in the Trifid Nebula, one of the youngest star forming regions

Recent magnetic field surveys in O- and B-type stars revealed that about 10% of the core-hydrogen-burning massive stars host large-scale magnetic fields. The physical origin of these fields is highly debated. To identify and model the physical processes responsible for the generation of magnetic fields in massive stars, it is important to establish whether magnetic massive stars are found in very young star-forming regions or whether they are formed in close interacting binary systems. In the framework of our ESO Large Program, we carried out low-resolution spectropolarimetric observations with FORS2 in 2013 April of the three most massive central stars in the Trifid nebula, HD164492A, HD164492C, and HD164492D. These observations indicated a strong longitudinal magnetic field of about 500-600G in the poorly studied component HD164492C. To confirm this detection, we used HARPS in spectropolarimetric mode on two consecutive nights in 2013 June. Our HARPS observations confirmed the longitudinal magnetic field in HD164492C. Furthermore, the HARPS observations revealed that HD164492C cannot be considered as a single star as it possesses one or two companions. The spectral appearance indicates that the primary is most likely of spectral type B1-B1.5V. Since in both observing nights most spectral lines appear blended, it is currently unclear which components are magnetic. Long-term monitoring using high-resolution spectropolarimetry is necessary to separate the contribution of each component to the magnetic signal. Given the location of the system HD164492C in one of the youngest star formation regions, this system can be considered as a Rosetta Stone for our understanding of the origin of magnetic fields in massive stars.Comment: Five pages, six figures, accepted for publication in A&

Equivalence of the Path Integral for Fermions in Cartesian and Spherical Coordinates

The path-integral calculation for the free energy of a spin-1/2 Dirac-fermion gas is performed in spherical polar coordinates for a flat spacetime geometry. Its equivalence with the Cartesian-coordinate representation is explicitly established. This evaluation involves a relevant limiting case of the fermionic path integral in a Schwarzschild background, whose near-horizon limit has been shown to be related to black hole thermodynamics.Comment: 16 page

Comments on Non-Commutative Phenomenology

It is natural to ask whether non-commutative geometry plays a role in four dimensional physics. By performing explicit computations in various toy models, we show that quantum effects lead to violations of Lorentz invariance at the level of operators of dimension three or four. The resulting constraints are very stringent.Comment: Correction of an error in the U(1) and U(N) calculation leads to stronger limits than those given previously Clarifying comments and reference adde