116990186
Essay: Supersymmetry, the Cosmological Constant, and a Theory of Quantum Gravity in Our Universe
There are many theories of quantum gravity, depending on asymptotic boundary conditions, and the amount of supersymmetry. The cosmological constant is one of the fundamental parameters that characterizes different theories. If it is positive, supersymmetry must be broken. A heuristic calculation shows that a cosmological constant of the observed size predicts superpartners in the TeV range. This mechanism for SUSY breaking also puts important constraints on low energy particle physics models.
14227515
Black Crunch
We study the growth of fluctuations in collapsing cosmologies, extending old work of Lifschitz and Khalatnikov. As examples of systems where the fluctuations have a different composition than the background we study scalar fields with general improvement terms. Fluctuations always grow, and often dominate the homogeneous background. We argue that even for very dilute fluctuations, scattering processes inevitably lead to a dense gas of black holes. This leads us to hypothesize that the generic final state of a Big Crunch is described by a collapsing p = ρ FRW cosmology. We conjecture that the black hole fluid is invariant under the conformal Killing symmetry of this metric, so that the final state is in fact stationary.
125302371
Cosmological SUSY Breaking and the Pyramid Scheme
17779961
Holographic cosmology 3.0
We present a new version of holographic cosmology, which is compatible with present observations. A primordial p = ρ phase of the universe is followed by a brief matter dominated era and a brief period of inflation, whose termination heats the universe. The flatness and horizon problems are solved by the p = ρ dynamics. The model is characterized by two parameters, which should be calculated in a more fundamental approach to the theory. For a large range in the phenomenologically allowed parameter space, the observed fluctuations in the cosmic microwave background were generated during the p = ρ era, and are exactly scale invariant. The scale invariant spectrum cuts off sharply at both upper and lower ends, and this may have observational consequences. We argue that the amplitude of fluctuations is small but cannot yet calculate it precisely.
120087716
Anharmonic Oscillator with Polynomial Self‐Interaction
A quantum anharmonic oscillator with a polynomial self‐interaction is defined in coordinate space by a Hamiltonian of the form H = −d2/dx2 + ¼x2 + g[(½x2)N + a(½x2)N−1 + b(½x2)N−2 + ⋯]. Using WKB techniques we derive a secular equation which determines the eigenvalues of H for small |g|. We find that the qualitative analytic structure of these eigenvalues as functions of complex g remains unchanged for all fixed values of a, b,…, including a = b = ⋯ = 0. The secular equation also implies an elegant theorem which predicts how the a,b,⋯ terms in H affect the large‐order growth of perturbation theory. We use this theorem to compare the perturbative behavior of non‐Wick‐ordered and Wick‐ordered field theories in one‐dimensional space‐time. In particular, we show that the perturbation series ∑Angn and ∑Bngn for the energy levels of the (gψ2N)1 and (:gψ2N:)1 field theories differ in large order by an over‐all multiplicative constant limn→∞An/Bn = exp[N(2N − 1)/(2N − 2)].
16630872
Some Thoughts on the Quantum Theory of de Sitter Space
This is a summary of two lectures I gave at the Davis Conference on Cosmic Inflation. I explain why the quantum theory of de Sitter (dS) space should have a finite number of states and explore gross aspects of the hypothetical quantum theory, which can be gleaned from semiclassical considerations. The constraints of a self-consistent measurement theory in such a finite system imply that certain mathematical features of the theory are unmeasurable, and that the theory is consequently mathematically ambiguous. There will be a universality class of mathematical theories all of whose members give the same results for local measurements, within the {\it a priori} constraints on the precision of those measurements, but make different predictions for unmeasurable quantities, such as the behavior of the system on its Poincare recurrence time scale. A toy model of dS quantum mechanics is presented.
119144377
A circulating hydrogen ultra-high purification system for the MuCap experiment
Abstract The MuCap experiment is a high-precision measurement of the rate for the basic electroweak process of muon capture, μ − +p→n+ ν μ . The experimental approach is based on an active target consisting of a time projection chamber (TPC) operating with pure hydrogen gas. The hydrogen has to be kept extremely pure and at a stable pressure. A Circulating Hydrogen Ultra-high Purification System was designed at the Petersburg Nuclear Physics Institute (PNPI) to continuously clean the hydrogen from impurities. The system is based on an adsorption cryo pump to stimulate the hydrogen flow and on a cold adsorbent for the hydrogen cleaning. It was installed at the Paul Scherrer Institute (PSI) in 2004 and performed reliably during three experiment runs. During several months long operating periods the system maintained the hydrogen purity in the detector on the level of 20 ppb for moisture, which is the main contaminant, and of better than 7 and 5 ppb for nitrogen and oxygen, respectively. The pressure inside the TPC was stabilized to within 0.024% of 10 bar at a hydrogen flow rate of three standard liters per minute.
73646575
Initial performance of the CUORE-0 experiment
CUORE-0 is a cryogenic detector that uses an array of tellurium dioxide bolometers to search for neutrinoless double-beta decay of $$\mathrm {^{130}Te}$$130Te. We present the first data analysis with $$7.1 \,\mathrm {kg\cdot y}$$7.1kg·y of total $$\mathrm {TeO_2}$$TeO2 exposure focusing on background measurements and energy resolution. The background rates in the neutrinoless double-beta decay region of interest (2.47 to $$2.57 \,\mathrm {MeV}$$2.57MeV) and in the $$\alpha $$α background-dominated region (2.70 to $$3.90\,\mathrm {MeV}$$3.90MeV) have been measured to be $${0.071\pm 0.011}$$0.071±0.011 and $${0.019\pm 0.002}\,\mathrm {counts/(keV\cdot kg\cdot y)}$$0.019±0.002counts/(keV·kg·y), respectively. The latter result represents a factor of 6 improvement from a predecessor experiment, Cuoricino. The results verify our understanding of the background sources in CUORE-0, which is the basis of extrapolations to the full CUORE detector. The obtained energy resolution (full width at half maximum) in the region of interest is $$5.7\,\mathrm {keV}$$5.7keV. Based on the measured background rate and energy resolution in the region of interest, CUORE-0 half-life sensitivity is expected to surpass the observed lower bound of Cuoricino with one year of live time.
118695560
First results from the MuLan and MuCap experiments
MuLan and MuCap are ongoing experiments at the Paul Scherrer Institut, Switzerland, that use the muon lifetime to determine fundamental weak interaction parameters. The goal of MuLan is a 1 ppm measurement of the positive muon lifetime τμ+ to determine the Fermi constant GF to 0.5 ppm. The goal of MuCap is to make a 1% determination of the rate ΛS of the process of nuclear muon capture by the proton, μp→nν, by measuring the μ− disappearance rate in hydrogen gas to 10 ppm and subtracting the world average for the μ+ decay rate. A 1% determination of the capture rate ΛS is of interest because it would enable a 7% determination of gP, the induced pseudoscalar coupling of the nucleon. In 2007, both experiments published first results based upon data collected by each in 2004. MuLan reported an 11 ppm μ+ lifetime measurement, τμ+ = 2.197 013(24) μs, resulting in a new, 9.6 ppm world average, τμ+ = 2.197 019(21) μs, which determines the Fermi constant, GF = 1.166 371(6)×10−5 GeV−2, to 5 ppm. MuCap reported a 3%...
85463997
The low energy spectrum of TeO2 bolometers: results and dark matter perspectives for the CUORE-0 and CUORE experiments
We collected 19.4 days of data from four 750g TeO2 bolometers, and in three of them we were able to set the energy threshold around 3 keV using a new analysis technique. We found a background rate ranging from 25 cpd/keV/kg at 3 keV to 2 cpd/keV/kg at 25 keV, and a peak at 4.7 keV. The origin of this peak is presently unknown, but its presence is confirmed by a reanalysis of 62.7 kg.days of data from the finished CUORICINO experiment. Finally, we report the expected sensitivities of the CUORE-0 (52 bolometers) and CUORE (988 bolometers) experiments to a WIMP annual modulation signal.
28501467
CUORE crystal validation runs: Results on radioactive contamination and extrapolation to CUORE background
The CUORE Crystal Validation Runs (CCVRs) have been carried out since the end of 2008 at the Gran Sasso National Laboratories, in order to test the performance and the radiopurity of the TeO2 crystals produced at SICCAS (Shanghai Institute of Ceramics, Chinese Academy of Sciences) for the CUORE experiment. In this work the results of the first 5 validation runs are presented. Results have been obtained for bulk contaminations and surface contaminations from several nuclides. An extrapolation to the CUORE background has been performed. (C) 2012 Elsevier B.V. All rights reserved.