35 research outputs found
First test of a cryogenic scintillation module with a CaWO4 scintillator and a low-temperature photomultiplier down to 6 K
Future cryogenic experiments searching for rare events require reliable,
efficient and robust techniques for the detection of photons at temperatures
well below that to which low-temperature photomultipliers (PMT) were
characterised. Motivated by this we investigated the feasibility of a
low-temperature PMT for the detection of scintillation from crystalline
scintillators at T = 6 K. The scintillation module was composed of a CaWO4
scintillator and a low-temperature PMT D745B from ET Enterprises. The PMT
responsivity was studied at T=290, 77 and 6 K using gamma-quanta from 241Am (60
keV) and 57Co (122 and 136 keV) sources. We have shown that the low-temperature
PMT retains its single photon counting ability even at cryogenic temperatures.
At T = 6 K, the response of the PMT decreases to 51 +- 13 % and 27 +- 6 % when
assessed in photon counting and pulse height mode, respectively. Due to the
light yield increase of the CaWO4 scintillating crystal the overall
responsivity of the scintillation modules CaWO4+PMT is 94 +- 15 % (photon
counting) and 48 +- 8 % (pulse height) when cooling to T = 6 K. The dark count
rate was found to be 20 s-1. The energy resolution of the module remains
similar to that measured at room temperature using either detection mode. It is
concluded that commercially available low-temperature PMT are well suited for
detection of scintillation light at cryogenic temperatures
The averaged tensors of the relative energy-momentum and angular momentum in general relativity and some their applications
There exist at least a few different kind of averaging of the differences of
the energy-momentum and angular momentum in normal coordinates {\bf NC(P)}
which give tensorial quantities. The obtained averaged quantities are
equivalent mathematically because they differ only by constant scalar
dimensional factors. One of these averaging was used in our papers [1-8] giving
the {\it canonical superenergy and angular supermomentum tensors}.
In this paper we present another averaging of the differences of the
energy-momentum and angular momentum which gives tensorial quantities with
proper dimensions of the energy-momentum and angular momentum densities. But
these averaged relative energy-momentum and angular momentum tensors, closely
related to the canonical superenergy and angular supermomentum tensors, {\it
depend on some fundamental length }.
The averaged relative energy-momentum and angular momentum tensors of the
gravitational field obtained in the paper can be applied, like the canonical
superenergy and angular supermomentum tensors, to {\it coordinate independent}
analysis (local and in special cases also global) of this field.
We have applied the averaged relative energy-momentum tensors to analyze
vacuum gravitational energy and momentum and to analyze energy and momentum of
the Friedman (and also more general) universes. The obtained results are very
interesting, e.g., the averaged relative energy density is {\it positive
definite} for the all Friedman universes.Comment: 30 pages, minor changes referring to Kasner universe
Brain Complexity: Analysis, Models and Limits of Understanding
Abstract. Manifold initiatives try to utilize the operational principles of organisms and brains to develop alternative, biologically inspired computing paradigms. This paper reviews key features of the standard method applied to complexity in the cognitive and brain sciences, i.e. decompositional analysis. Projects investigating the nature of computations by cortical columns are discussed which exemplify the application of this standard method. New findings are mentioned indicating that the concept of the basic uniformity of the cortex is untenable. The claim is discussed that non-decomposability is not an intrinsic property of complex, integrated systems but is only in our eyes, due to insufficient mathematical techniques. Using Rosen’s modeling relation, the scientific analysis method itself is made a subject of discussion. It is concluded that the fundamental assumption of cognitive science, i.e., cognitive and other complex systems are decomposable, must be abandoned.
Long-Baseline Neutrino Facility (LBNF) and Deep Underground Neutrino Experiment (DUNE) Conceptual Design Report Volume 2: The Physics Program for DUNE at LBNF
The Physics Program for the Deep Underground Neutrino Experiment (DUNE) at the Fermilab Long-Baseline Neutrino Facility (LBNF) is described
Relative Energy-Momentum of the Bianchi-I Type Universes in Teleparallel Gravity
This paper has been removed by arXiv administrators because it plagiarizes
gr-qc/0011027, gr-qc/0205028, and gr-qc/0303034.Comment: This submission has been withdrawn by arXiv administrators due to
inappropriate text reuse from external source