Is it possible to accommodate massive photons in the framework of a gauge-invariant electrodynamics?

The construction of an alternative electromagnetic theory that preserves Lorentz and gauge symmetries, is considered. We start off by building up Maxwell electrodynamics in (3+1)D from the assumption that the associated Lagrangian is a gauge-invariant functional that depends on the electron and photon fields and their first derivatives only. In this scenario, as well-known, it is not possible to set up a Lorentz invariant gauge theory containing a massive photon. We show nevertheless that there exist two radically different electrodynamics, namely, the Chern-Simons and the Podolsky formulations, in which this problem can be overcome. The former is only valid in odd space-time dimensions, while the latter requires the presence of higher-order derivatives of the gauge field in the Lagrangian. This theory, usually known as Podolsky electrodynamics, is simultaneously gauge and Lorentz invariant; in addition, it contains a massive photon. Therefore, a massive photon, unlike the popular belief, can be adequately accommodated within the context of a gauge-invariant electrodynamics.Comment: 10 page

Whirling Waves and the Aharonov-Bohm Effect for Relativistic Spinning Particles

The formulation of Berry for the Aharonov-Bohm effect is generalized to the relativistic regime. Then, the problem of finding the self-adjoint extensions of the (2+1)-dimensional Dirac Hamiltonian, in an Aharonov-Bohm background potential, is solved in a novel way. The same treatment also solves the problem of finding the self-adjoint extensions of the Dirac Hamiltonian in a background Aharonov-Casher

Recent progress of GaAsP HPD development for the MAGIC telescope project

Today the Hybrid Photon Detector (HPD) is one of the few low light level (LLL) sensors that can provide an excellent single and multiple photoelectron (ph.e.) amplitude resolution. The recently developed HPDs for the MAGIC telescope project with a GaAsP photocathode, namely the R9792U-40, provide a peak quantum efficiency (QE) of more than 50% and a pulse width of ~2 nsec. In addition, the afterpulsing rate of these tubes is very low compared to that of conventional photomultiplier tubes (PMTs), i.e. the value is ~300 times lower. Photocathode aging measurements showed life time of more than 10 years under standard operating conditions of the Cherenkov Telescopes. Here we want to report on the recent progress with the above mentioned HPDs.Comment: Contribution to the 30th ICRC, Merida Mexico, July 2007 on behalf of the MAGIC Collaboratio

Berry phases and zero-modes in toroidal topological insulator

An effective Hamiltonian describing the surface states of a toroidal topological insulator is obtained, and it is shown to support both bound-states and charged zero-modes. Actually, the spin connection induced by the toroidal curvature can be viewed as an position-dependent effective vector potential, which ultimately yields the zero-modes whose wave-functions harmonically oscillate around the toroidal surface. In addition, two distinct Berry phases are predicted to take place by the virtue of the toroidal topology.Comment: New version, accepted for publication in EPJB, 6 pages, 1 figur

Sobrevivência e desenvolvimento larval de Spodoptera frugiperda (J E Smith) (Lepidoptera: Noctuidae) em hospedeiros alternativos.

Dois bioensaios foram conduzidos para avaliar a adaptação da lagarta-do-cartucho (LCM), Spodoptera frugiperda (J E Smith), em alguns de seus hospedeiros mais comuns nos agroecossistemas brasileiros. Em testes de confi namento, utilizando lagartas recém-eclodidas e seções de folhas de milho (Zea mays), sorgo granífero (Sorghum bicolor), sorgo selvagem (Sorghum sp.), braquiária Brachiaria sp., soja (Glycine max) e fumo (Nicotiana tabacum), foram observados a sobrevivência e o desenvolvimento larval da LCM. A sobrevivência da LCM nos diferentes hospedeiros foi acima de 80%, exceto nas folhas de fumo, que foi nula. O acúmulo de biomassa nas lagartas desenvolvidas na soja e na dieta artifi cial foi maior do que nos demais hospedeiros. A maior biomassa foi das pupas de lagartas alimentadas na dieta artifi cial e a menor nas lagartas e pupas provenientes da braquiária. A menor média do período larval foi dos insetos desenvolvidos no milho e a maior nos alimentados na dieta artifi cial Foram observadas três classes de período larval no milho; quatro no sorgo, na braquiária e na soja e cinco na dieta artifi cial As porcentagens aproximadas dos indivíduos da LCM que completaram o período larval foram 85% até o 12o. dia em milho; 77% em sorgo granífero, 80% em sorgo selvagem, 83% em soja e 68% em braquiária, até o 14o dia; e 69% na dieta artifi cial até o 17o dia. Portanto, a adaptação da LCM foi melhor no milho, intermediária no sorgo e na soja e pior na braquiária