935 research outputs found
Active Galactic Nuclei with Starbursts: Sources for Ultra High Energy Cosmic Rays
Ultra high energy cosmic ray events presently show a spectrum, which we
interpret here as galactic cosmic rays due to a starburst in the radio galaxy
Cen A pushed up in energy by the shock of a relativistic jet. The knee feature
and the particles with energy immediately higher in galactic cosmic rays then
turn into the bulk of ultra high energy cosmic rays. This entails that all
ultra high energy cosmic rays are heavy nuclei. This picture is viable if the
majority of the observed ultra high energy events come from the radio galaxy
Cen A, and are scattered by intergalactic magnetic fields across most of the
sky.Comment: 4 pages, 1 figure, proceedings of "High-Energy Gamma-rays and
Neutrinos from Extra-Galactic Sources", Heidelber
Conformal field theories with infinitely many conservation laws
Globally conformal invariant quantum field theories in a D-dimensional
space-time (D even) have rational correlation functions and admit an infinite
number of conserved (symmetric traceless) tensor currents. In a theory of a
scalar field of dimension D-2 they were demonstrated to be generated by bilocal
normal products of free massless scalar fields with an O(N), U(N), or Sp(2N)
(global) gauge symmetry [BNRT].
Recently, conformal field theories "with higher spin symmetry" were
considered for D=3 in [MZ] where a similar result was obtained (exploiting
earlier study of CFT correlators). We suggest that the proper generalization of
the notion of a 2D chiral algebra to arbitrary (even or odd) dimension is
precisely a CFT with an infinite series of conserved currents. We shall recast
and complement (part of) the argument of Maldacena and Zhiboedov into the
framework of our earlier work. We extend to D=4 the auxiliary Weyl-spinor
formalism developed in [GPY] for D=3. The free field construction only follows
for D>3 under additional assumptions about the operator product algebra. In
particular, the problem of whether a rational CFT in 4D Minkowski space is
necessarily trivial remains open.Comment: 24 pages, Lecture at the TH Journal Club (CERN, February 2012
Solar panels as air Cherenkov detectors for extremely high energy cosmic rays
Increasing interest towards the observation of the highest energy cosmic rays
has motivated the development of new detection techniques. The properties of
the Cherenkov photon pulse emitted in the atmosphere by these very rare
particles indicate low-cost semiconductor detectors as good candidates for
their optical read-out.
The aim of this paper is to evaluate the viability of solar panels for this
purpose. The experimental framework resulting from measurements performed with
suitably-designed solar cells and large conventional photovoltaic areas is
presented.
A discussion on the obtained and achievable sensitivities follows.Comment: 6 pages, 8 eps figures included with epsfig, uses espcrc2.sty. Talk
given at the Sixth Topical Seminar on Neutrino and Astroparticle Physics, San
Miniato, Italy, 17-21 May 199
Chiral Supersymmetric Gepner Model Orientifolds
We explicitly construct A-type orientifolds of supersymmetric Gepner models.
In order to reduce the tadpole cancellation conditions to a treatable number we
explicitly work out the generic form of the one-loop Klein bottle, annulus and
Moebius strip amplitudes for simple current extensions of Gepner models.
Equipped with these formulas, we discuss two examples in detail to provide
evidence that in this setting certain features of the MSSM like unitary gauge
groups with large enough rank, chirality and family replication can be
achieved.Comment: 37 pages, TeX (harvmac), minor changes, typos corrected, to appear in
JHE
Four Dimensional CFT Models with Rational Correlation Functions
Recently established rationality of correlation functions in a globally
conformal invariant quantum field theory satisfying Wightman axioms is used to
construct a family of soluble models in 4-dimensional Minkowski space-time. We
consider in detail a model of a neutral scalar field of dimension 2. It
depends on a positive real parameter c, an analogue of the Virasoro central
charge, and admits for all (finite) c an infinite number of conserved symmetric
tensor currents. The operator product algebra of is shown to coincide
with a simpler one, generated by a bilocal scalar field of
dimension (1,1). The modes of V together with the unit operator span an
infinite dimensional Lie algebra whose vacuum (i.e. zero energy lowest
weight) representations only depend on the central charge c. Wightman
positivity (i.e. unitarity of the representations of ) is proven to be
equivalent to .Comment: 28 pages, LATEX, amsfonts, latexsym. Proposition 2.3, and Conjecture
in Sec. 6 are revised. Minor errors are correcte
Ultra-High Energy Cosmic Rays from Young Neutron Star Winds
The long-held notion that the highest-energy cosmic rays are of distant
extragalactic origin is challenged by observations that events above eV do not exhibit the expected high-energy cutoff from photopion
production off the cosmic microwave background. We suggest that these
unexpected ultra-high-energy events are due to iron nuclei accelerated from
young strongly magnetized neutron stars through relativistic MHD winds. We find
that neutron stars whose initial spin periods are shorter than ms, where is the surface magnetic field, can
accelerate iron cosmic rays to greater than eV. These ions can
pass through the remnant of the supernova explosion that produced the neutron
star without suffering significant spallation reactions. For plausible models
of the Galactic magnetic field, the trajectories of the iron ions curve
sufficiently to be consistent with the observed arrival directions of the
highest energy events.Comment: 11 pages, 1 figure, replaced with revised version, some references
adde
- …