9,075 research outputs found
Gravitational trapping potential with arbitrary extra dimensions
We extend a recently discovered, non-singular 6 dimensional brane, solution
to D=4+n dimensions. As with the previous 6D solution the present solution
provides a gravitational trapping mechanism for fields of spin 0, 1/2, 1 and 2.
There is an important distinction between 2 extra dimensions and extra
dimensions that makes this more than a trivial extension. In contrast to
gravity in n >2 dimensions, gravity in n=2 dimensions is conformally flat. The
stress-energy tensor required by this solution has reasonable physically
properties, and for n=2 and n=3 can be made to asymptotically go to zero as one
moves away from the brane.Comment: 7 pages revtex. No figures. References added some discussions change
Photovoltaic Current Response of Mesoscopic Conductors to Quantized Cavity Modes
We extend the analysis of the effects of electromagnetic (EM) fields on
mesoscopic conductors to include the effects of field quantization, motivated
by recent experiments on circuit QED. We show that in general there is a
photovoltaic (PV) current induced by quantized cavity modes at zero bias across
the conductor. This current depends on the average photon occupation number and
vanishes identically when it is equal to the average number of thermal
electron-hole pairs. We analyze in detail the case of a chaotic quantum dot at
temperature T_e in contact with a thermal EM field at temperature T_f,
calculating the RMS size of the PV current as a function of the temperature
difference, finding an effect ~pA.Comment: 4 pages, 2 figure
Classical and nonclassical randomness in quantum measurements
The space of positive operator-valued measures on the Borel sets of a compact
(or even locally compact) Hausdorff space with values in the algebra of linear
operators acting on a d-dimensional Hilbert space is studied from the
perspectives of classical and non-classical convexity through a transform
that associates any positive operator-valued measure with a certain
completely positive linear map of the homogeneous C*-algebra
into . This association is achieved by using an operator-valued integral
in which non-classical random variables (that is, operator-valued functions)
are integrated with respect to positive operator-valued measures and which has
the feature that the integral of a random quantum effect is itself a quantum
effect. A left inverse for yields an integral representation,
along the lines of the classical Riesz Representation Theorem for certain
linear functionals on , of certain (but not all) unital completely
positive linear maps . The extremal and
C*-extremal points of the space of POVMS are determined.Comment: to appear in Journal of Mathematical Physic
Ultra-high energy neutrino scattering
Estimates are made of the ultra-high energy neutrino cross sections based on
an extrapolation to very small Bjorken x of the logarithmic Froissart
dependence in x shown previously to provide an excellent fit to the measured
proton structure function F_2^p(x,Q^2) over a broad range of the virtuality
Q^2. Expressions are obtained for both the neutral current and the charged
current cross sections. Comparison with an extrapolation based on perturbative
QCD shows good agreement for energies where both fit data, but our rates are as
much as a factor of 10 smaller for neutrino energies above 10^9 GeV, with
important implications for experiments searching for extra-galactic neutrinos.Comment: 4 pages, 1 figure, 1 table; Title, abstract and text changed,
conclusions unchanged. Version accepted for publication in Physical Review
Recommended from our members
The View of Russian Students on Whether Psychology is a Science
The Psychology as Science Scale (Friedrich, 1996) was administered to 525 psychology students from nine Russian universities to assess their beliefs about the nature of the discipline. About half of students (49.6%) generally agreed that psychology may be called a scientific discipline. Specifically, 71. 5% of the students agreed that psychology is a natural science, similar to biology, chemistry, and physics, 39. 9% of students agreed that psychological research is important and training in psychological methodology is necessary, and 43.1% of students agreed that human behavior is highly predictable. Students who took three methodology courses shared significantly stronger beliefs in the need for psychological research and the importance of training in methodology compared to students who did not take any methodology courses. Furthermore, students with a specialist degree had significantly stronger beliefs that psychology is a science compared to students who have just finished school. In terms of the effect of students’ career aspirations, students who wanted to be academic psychologists and clinicians had significantly stronger beliefs that psychology is a science compared to students who did not have clarity about their future careers. Regardless of the study limitations, these findings have potential implications for Russian psychology instructors
Orientifolds of Gepner Models
We systematically construct and study Type II Orientifolds based on Gepner
models which have N=1 supersymmetry in 3+1 dimensions. We classify the parity
symmetries and construct the crosscap states. We write down the conditions that
a configuration of rational branes must satisfy for consistency (tadpole
cancellation and rank constraints) and spacetime supersymmetry. For certain
cases, including Type IIB orientifolds of the quintic and a two parameter
model, one can find all solutions in this class. Depending on the parity, the
number of vacua can be large, of the order of 10^{10}-10^{13}. For other
models, it is hard to find all solutions but special solutions can be found --
some of them are chiral. We also make comparison with the large volume regime
and obtain a perfect match. Through this study, we find a number of new
features of Type II orientifolds, including the structure of moduli space and
the change in the type of O-planes under navigation through non-geometric
phases.Comment: 142 page
Gauge invariance of dimension two condensate in Yang-Mills theory
Gauge independence of dimension two condensate in Yang-Mills theory is
demonstrated by using a noncommutative theory technique.Comment: 7 page
Semiclassical approach to the decay of protons in circular motion under the influence of gravitational fields
We investigate the possible decay of protons in geodesic circular motion
around neutral compact objects. Weak and strong decay rates and the associated
emitted powers are calculated using a semi-classical approach. Our results are
discussed with respect to distinct ones in the literature, which consider the
decay of accelerated protons in electromagnetic fields. A number of consistency
checks are presented along the paper.Comment: To appear in Physical Review
Some New/Old Approaches to QCD
This is a talk delivered at the Meeting on Integrable Quantum Field Theories,
Villa Olmo and at STRINGS 1992, Rome, September 1992. I discuss some recent
attempts to revive two old ideas regarding an analytic approach to QCD-the
development of a string representation of the theory and the large N limit of
QCD.Comment: 20 page
- …