Neutrino flavor ratios as diagnostic of solar WIMP annihilation

We consider the neutrino (and antineutrino) flavors arriving at Earth for neutrinos produced in the annihilation of weakly interacting massive particles (WIMPs) in the Sun's core. Solar-matter effects on the flavor propagation of the resulting \agt GeV neutrinos are studied analytically within a density-matrix formalism. Matter effects, including mass-state level-crossings, influence the flavor fluxes considerably. The exposition herein is somewhat pedagogical, in that it starts with adiabatic evolution of single flavors from the Sun's center, with $\theta_{13}$ set to zero, and progresses to fully realistic processing of the flavor ratios expected in WIMP decay, from the Sun's core to the Earth. In the fully realistic calculation, non-adiabatic level-crossing is included, as are possible nonzero values for $\theta_{13}$ and the CP-violating phase $\delta$. Due to resonance enhancement in matter, nonzero values of $\theta_{13}$ even smaller than a degree can noticeably affect flavor propagation. Both normal and inverted neutrino-mass hierarchies are considered. Our main conclusion is that measuring flavor ratios (in addition to energy spectra) of \agt GeV solar neutrinos can provide discrinination between WIMP models. In particular, we demonstrate the flavor differences at Earth for neutrinos from the two main classes of WIMP final states, namely $W^+ W^-$ and 95% $b \bar{b}$ + 5% $\tau^+\tau^-$. Conversely, if WIMP properties were to be learned from production in future accelerators, then the flavor ratios of \agt GeV solar neutrinos might be useful for inferring $\theta_{13}$ and the mass hierarchy.Comment: 30 pages, including 10 figures and 4 appendice

Synchronization in heterogeneous FitzHugh-Nagumo networks with hierarchical architecture

We study synchronization in heterogeneous FitzHugh-Nagumo networks. It is well known that heterogeneities in the nodes hinder synchronization when becoming too large. Here, we develop a controller to counteract the impact of these heterogeneities. We first analyze the stability of the equilibrium point in a ring network of heterogeneous nodes. We then derive a sufficient condition for synchronization in the absence of control. Based on these results we derive the controller providing synchronization for parameter values where synchronization without control is absent. We demonstrate our results in networks with different topologies. Particular attention is given to hierarchical (fractal) topologies, which are relevant for the architecture of the brain

Cavity quantum acoustic device in the multimode strong coupling regime

We investigate an acoustical analog of circuit quantum electrodynamics that facilitates compact high-Q (${>}20,000$) microwave-frequency cavities with dense spectra. We fabricate and characterize a device that comprises a flux tunable transmon coupled to a $300\,\mathrm{\mu m}$ long surface acoustic wave resonator. For some modes, the qubit-cavity coupling reaches $6.5\,\mathrm{MHz}$, exceeding the cavity loss rate ($200\,\mathrm{kHz}$), qubit linewidth ($1.1\,\mathrm{MHz}$), and the cavity free spectral range ($4.8\,\mathrm{MHz}$), placing the device in both the strong coupling and strong multimode regimes. With the qubit detuned from the cavity, we show that the dispersive shift behaves according to predictions from a generalized Jaynes-Cummings Hamiltonian. Finally, we observe that the qubit linewidth strongly depends on its frequency, as expected for spontaneous emission of phonons, and we identify operating frequencies where this emission rate is suppressed

The detection of FIR emission from high redshift star-forming galaxies in the ECDF-S

ABRIDGED: We have used the LABOCA Survey of the ECDF-S (LESS) to investigate rest-frame FIR emission from typical SF systems (LBGs) at redshift 3, 4, and 5. We initially concentrate on LBGs at z~3 and select three subsamples on stellar mass, extinction corrected SF and rest-frame UV-magnitude. We produce composite 870micron images of the typical source in our subsamples, obtaining ~4sigma detections and suggesting a correlation between FIR luminosity and stellar mass. We apply a similar procedure to our full samples at z~3, 4, 4.5 and 5 and do not obtain detections - consistent with a simple scaling between FIR luminosity and stellar mass. In order to constrain the FIR SED of these systems we explore their emission at multiple wavelengths spanning the peak of dust emission at z~3 using the Herschel SPIRE observations of the field. We obtain detections at multiple wavelengths for both our stellar mass and UV-magnitude selected samples, and find a best-fit SED with T_dust in the ~33-41K range. We calculate L_FIR, obscured SFRs and M_dust, and find that a significant fraction of SF in these systems is obscured. Interestingly, our extinction corrected SFR sample does not display the large FIR fluxes predicted from its red UV-spectral slope. This suggests that the method of assuming an intrinsic UV-slope and correcting for dust attenuation may be invalid for this sample - and that these are not in fact the most actively SF systems. All of our z~3 samples fall on the `main sequence' of SF galaxies at z~3 and our detected subsamples are likely to represent the high obscuration end of LBGs at their epoch. We compare the FIR properties of our subsamples with various other populations, finding that our stellar mass selected sample shows similar FIR characteristics to SMGs at the same epoch and therefore potentially represents the low L_FIR end of the high redshift FIR luminosity function.Comment: 18 pages, 10 figure, MNRAS accepted, corrected typos, acknowledgements adde

The slowing down of galaxy disks in dissipationless minor mergers

We have investigated the impact of dissipationless minor galaxy mergers on the angular momentum of the remnant. Our simulations cover a range of initial orbital characteristics and the system consists of a massive galaxy with a bulge and disk merging with a much less massive (one-tenth or one-twentieth) gasless companion which has a variety of morphologies (disk- or elliptical-like) and central baryonic mass concentrations. During the process of merging, the orbital angular momentum is redistributed into the internal angular momentum of the final system; the internal angular momentum of the primary galaxy can increase or decrease depending on the relative orientation of the orbital spin vectors (direct or retrograde), while the initially non-rotating dark matter halo always gains angular momentum. The specific angular momentum of the stellar component always decreases independent of the orbital parameters or morphology of the satellite, the decrease in the rotation velocity of the primary galaxy is accompanied by a change in the anisotropy of the orbits, and the ratio of rotation speed to velocity dispersion of the merger remnant is lower than the initial value, not only due to an increase in the dispersion but also to the slowing -down of the disk rotation. We briefly discuss several astrophysical implications of these results, suggesting that minor mergers do not cause a "random walk" process of the angular momentum of the stellar disk component of galaxies, but rather a steady decrease. Minor mergers may play a role in producing the large scatter observed in the Tully-Fisher relation for S0 galaxies, as well as in the increase of the velocity dispersion and the decrease in $v/\sigma$ at large radii as observed in S0 galaxies.Comment: 10 pages, 10 figures, accepted for publication in A&