Massive photons and Lorentz violation

All quadratic translation- and gauge-invariant photon operators for Lorentz breakdown are included into the Stueckelberg Lagrangian for massive photons in a generalized \xi-gauge. The corresponding dispersion relation and tree-level propagator are determined exactly, and some leading-order results are derived. The question of how to include such Lorentz-violating effects into a perturbative quantum-field expansion is addressed. Applications of these results within Lorentz-breaking quantum field theories include the regularization of infrared divergences as well as the free propagation of massive vector bosons.Comment: 12 pages, 1 figur

CPT and Lorentz-invariance violation

The largest gap in our understanding of nature at the fundamental level is perhaps a unified description of gravity and quantum theory. Although there are currently a variety of theoretical approaches to this question, experimental research in this field is inhibited by the expected Planck-scale suppression of quantum-gravity effects. However, the breakdown of spacetime symmetries has recently been identified as a promising signal in this context: a number of models for underlying physics can accommodate minuscule Lorentz and CPT violation, and such effects are amenable to ultrahigh-precision tests. This presentation will give an overview of the subject. Topics such as motivations, the SME test framework, mechanisms for relativity breakdown, and experimental tests will be reviewed. Emphasis is given to observations involving antimatter.Comment: 6 page

Can galaxy growth be sustained through HI-rich minor mergers?

Local galaxies with specific star-formation rates (star-formation rate per unit mass; sSFR~0.2-10/Gyr) as high as distant galaxies (z~1-3), are very rich in HI. Those with low stellar masses, log M_star (M_sun)=8-9, for example, have M_HI/M_star~5-30. Using continuity arguments of Peng et al. (2014), whereby the specific merger rate is hypothesized to be proportional to the specific star-formation rate, and HI gas mass measurements for local galaxies with high sSFR, we estimate that moderate mass galaxies, log M_star (M_sun)=9-10.5, can acquire sufficient gas through minor mergers (stellar mass ratios ~4-100) to sustain their star formation rates at z~2. The relative fraction of the gas accreted through minor mergers declines with increasing stellar mass and for the most massive galaxies considered, log M_star (M_sun)=10.5-11, this accretion rate is insufficient to sustain their star formation. We checked our minor merger hypothesis at z=0 using the same methodology but now with relations for local normal galaxies and find that minor mergers cannot account for their specific growth rates, in agreement with observations of HI-rich satellites around nearby spirals. We discuss a number of attractive features, like a natural down-sizing effect, in using minor mergers with extended HI disks to support star formation at high redshift. The answer to the question posed by the title, "Can galaxy growth be sustained through \HI-rich minor mergers?", is maybe, but only for relatively low mass galaxies and at high redshift.Comment: 6 pages, 3 figures; in final acceptance by A&

Estimate of heating effects in Raman microspectroscopy and the accuracy of stokes/anti-stokes thermometry

Нагрев образца значительно увеличивает неопределенность условий получения спектров в Рамановской микроспектроскопии. В работе теоретически оценен максимальный рост температуры внутри образца при воздействии лазерного излучения. Результат моделирования роста температуры представлен аналитически в виде функции свойств пробы (показатель рефракции, коэффициент абсорбции, теплопроводность), мощности лазера и значения апертуры фокусирующего объектива. Показано, что достигаемая точность определения температуры по соотношению интенсивностей стоксовской и антистоксовских полос может быть оценена теоретически, что имеет большую практическую значимость. Получена функциональная зависимость, связывающая точность определения температуры образца с основными источниками экспериментальных погрешностей. Обсуждены различные практически влияющие факторы, вызывающие ухудшение теоретического отношения dТ/Т

Conservation status and threats of Rallidae : a global assessment.

The avian family Rallidae is one of the most widespread avian families of the world. Rallidae greatly exceeds the other families within the order Gruiformes in sheer number of species, taxonomic complexity, geographical distribution, and ecological niche. At the time of this writing, there is no comprehensive, readily accessible, and up-to-date compilation of the conservation status of the world's rallids. This thesis provides a brief global overview of the status of rallids worldwide, focusing primarily on regional endemics and threatened species, and identifies the main threats and the associated particular knowledge gaps. The International Union for the Conservation of Nature (IUCN) Red List has a vast database of plants and animals found worldwide. The Red List Index (RLI) measures trends in regards to the risk of extinction; the data available for Rallidae species provides a broad measure of the overall population trend for some of the more cooperative, readily accessible, or targeted species. For many rallids, this is the only current trend indicator available on a regional or global basis. Data of avian families of similar size, equivalent global distributions, and similar lifestyles were also obtained from the RLI to compare for conservation status and population trends to place the circumstances of rallids in context; the families chosen were Anatidae, Cuculidae, Alcedinidae, and Corvidae. A chi-squared test showed significant (p<0.05) differences when comparing Rallidae population trends and conservation status to these four families. Listed threats to Rallidae were obtained from the IUCN and literature searches for the family and species listed as threatened. A chi-squared test showed a significant (p<0.05) number of insular species to have a threatened conservation status when compared to widespread species. Further focus was primarily on endemic and near-endemic species due to the inherent risk to these species as a result of their life history. Invasive species and habitat degradation or destruction were the primary threats identified. Wetland conservation is of special concern, as the majority of Rallidae species utilize this habitat. Internationally designated Important Bird Areas, Endemic Bird Areas, and associated sites designated under the Ramsar Convention were searched for mentions of rallids. In conclusion, Rallidae species are understudied and vast gaps in knowledge exist, particularly for species in remote locations and developing countries. The majority of rallids classified as Least Concern have decreasing or unknown population trends and should be reclassified as Data Deficient until more research is undertaken. The eradication of invasive species, particularly of mammalian predators, is essential to many endemic and near-endemic species recoveries. Habitat protections headed by BirdLife International and the Ramsar Convention are making headway worldwide, and with further research and environmental action the future of Rallidae is in turn better understood and protected

Dissecting the complex environment of a distant quasar with MUSE

High redshift quasars can be used to trace the early growth of massive galaxies and may be triggered by galaxy-galaxy interactions. We present MUSE science verification data on one such interacting system consisting of the well-studied z=3.2 PKS1614+051 quasar, its AGN companion galaxy and bridge of material radiating in Lyalpha between the quasar and its companion. We find a total of four companion galaxies (at least two galaxies are new discoveries), three of which reside within the likely virial radius of the quasar host, suggesting that the system will evolve into a massive elliptical galaxy by the present day. The MUSE data are of sufficient quality to split the extended Lyalpha emission line into narrow velocity channels. In these the gas can be seen extending towards each of the three neighbouring galaxies suggesting that the emission-line gas originates in a gravitational interaction between the galaxies and the quasar host. The photoionization source of this gas is less clear but is probably dominated by the two AGN. The quasar's Lyalpha emission spectrum is double-peaked, likely due to absorbing neutral material at the quasar's systemic redshift with a low column density as no damping wings are present. The spectral profiles of the AGN and bridge's Lyalpha emission are also consistent with absorption at the same redshift indicating this neutral material may extend over > 50 kpc. The fact that the neutral material is seen in the line of sight to the quasar and transverse to it, and the fact that we see the quasar and it also illuminates the emission-line bridge, suggests the quasar radiates isotropically and any obscuring torus is small. These results demonstrate the power of MUSE for investigating the dynamics of interacting systems at high redshift.Comment: 9 pages, 6 figures, published in MNRA

Resolving Phonon Fock States in a Multimode Cavity with a Double-Slit Qubit

We resolve phonon number states in the spectrum of a superconducting qubit coupled to a multimode acoustic cavity. Crucial to this resolution is the sharp frequency dependence in the qubit-phonon interaction engineered by coupling the qubit to surface acoustic waves in two locations separated by $\sim40$ acoustic wavelengths. In analogy to double-slit diffraction, the resulting self-interference generates high-contrast frequency structure in the qubit-phonon interaction. We observe this frequency structure both in the coupling rate to multiple cavity modes and in the qubit spontaneous emission rate into unconfined modes. We use this sharp frequency structure to resolve single phonons by tuning the qubit to a frequency of destructive interference where all acoustic interactions are dispersive. By exciting several detuned yet strongly-coupled phononic modes and measuring the resulting qubit spectrum, we observe that, for two modes, the device enters the strong dispersive regime where single phonons are spectrally resolved.Comment: 9 pages, 8 figures; revised arguments in paragraphs 3 and 8, added Hamiltonian description, and corrected typo