7,219 research outputs found
W(h)ither the Fed’s balance sheet?
Federal Reserve policymakers have expressed their support for ultimately shrinking the Fed’s balance sheet and returning the composition of its portfolio to only Treasury securities. Policymakers also favor returning to a fed-funds-rate-targeting procedure or something quite similar. While Fed holdings of some asset classes have been diminishing naturally, the orderly reduction of others could involve special tools that the Fed has been putting in place for a while. An ongoing issue will be to determine an optimal sequence of appropriate actions.Monetary policy - United States ; Federal Reserve System ; Financial crises
Improved Limit on theta_{13} and Implications for Neutrino Masses in Neutrino-less Double Beta Decay and Cosmology
We analyze the impact of a measurement, or of an improved bound, on
theta_{13} for the determination of the effective neutrino mass in
neutrino-less double beta decay and cosmology. In particular, we discuss how an
improved limit on (or a specific value of) theta_{13} can influence the
determination of the neutrino mass spectrum via neutrino-less double beta
decay. We also discuss the interplay with improved cosmological neutrino mass
searches.Comment: 22 pages, 5 figures. Minor corrections, matches version in PR
Quark-lepton mass unification at TeV scales
A scenario combining a model of early (TeV) unification of quarks and leptons
with the physics of large extra dimensions provides a natural mechanism linking
quark and lepton masses at TeV scale. This has been dubbed as early
quark-lepton mass unification by one of us (PQH) in one of the two models of
early quark-lepton unification, which are consistent with data, namely SU(4)_PS
\otimes SU(2)_L \otimes SU(2)_R \otimes SU(2)_H. In particular, it focused on
the issue of naturally light Dirac neutrino. The present paper will focus on
similar issues in the other model, namely SU(4)_PS \otimes SU(3)_L \otimes
SU(3)_H.Comment: Accepted for publication in PRD: The new version is in agreement with
the accepted manuscrip
En-route to the fission-fusion reaction mechanism: a status update on laser-driven heavy ion acceleration
The fission-fusion reaction mechanism was proposed in order to generate
extremely neutron-rich nuclei close to the waiting point N = 126 of the rapid
neutron capture nucleosynthesis process (r-process). The production of such
isotopes and the measurement of their nuclear properties would fundamentally
help to increase the understanding of the nucleosynthesis of the heaviest
elements in the universe. Major prerequisite for the realization of this new
reaction scheme is the development of laser-based acceleration of ultra-dense
heavy ion bunches in the mass range of A = 200 and above. In this paper, we
review the status of laser-driven heavy ion acceleration in the light of the
fission-fusion reaction mechanism. We present results from our latest
experiment on heavy ion acceleration, including a new milestone with
laser-accelerated heavy ion energies exceeding 5 MeV/u
Attosecond double-slit experiment
A new scheme for a double-slit experiment in the time domain is presented.
Phase-stabilized few-cycle laser pulses open one to two windows (``slits'') of
attosecond duration for photoionization. Fringes in the angle-resolved energy
spectrum of varying visibility depending on the degree of which-way information
are observed. A situation in which one and the same electron encounters a
single and a double slit at the same time is discussed. The investigation of
the fringes makes possible interferometry on the attosecond time scale. The
number of visible fringes, for example, indicates that the slits are extended
over about 500as.Comment: 4 figure
Bi-Laplacian Growth Patterns in Disordered Media
Experiments in quasi 2-dimensional geometry (Hele Shaw cells) in which a
fluid is injected into a visco-elastic medium (foam, clay or
associating-polymers) show patterns akin to fracture in brittle materials, very
different from standard Laplacian growth patterns of viscous fingering. An
analytic theory is lacking since a pre-requisite to describing the fracture of
elastic material is the solution of the bi-Laplace rather than the Laplace
equation. In this Letter we close this gap, offering a theory of bi-Laplacian
growth patterns based on the method of iterated conformal maps.Comment: Submitted to PRL. For further information see
http://www.weizmann.ac.il/chemphys/ander
Autonomous stochastic resonance in fully frustrated Josephson-junction ladders
We investigate autonomous stochastic resonance in fully frustrated
Josephson-junction ladders, which are driven by uniform constant currents. At
zero temperature large currents induce oscillations between the two ground
states, while for small currents the lattice potential forces the system to
remain in one of the two states. At finite temperatures, on the other hand,
oscillations between the two states develop even below the critical current;
the signal-to-noise ratio is found to display array-enhanced stochastic
resonance. It is suggested that such behavior may be observed experimentally
through the measurement of the staggered voltage.Comment: 6 pages, 11 figures, to be published in Phys. Rev.
Anomalous diffusion in viscosity landscapes
Anomalous diffusion is predicted for Brownian particles in inhomogeneous
viscosity landscapes by means of scaling arguments, which are substantiated
through numerical simulations. Analytical solutions of the related
Fokker-Planck equation in limiting cases confirm our results. For an ensemble
of particles starting at a spatial minimum (maximum) of the viscous damping we
find subdiffusive (superdiffusive) motion. Superdiffusion occurs also for a
monotonically varying viscosity profile. We suggest different substances for
related experimental investigations.Comment: 15 page
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