11,670 research outputs found
Secondary homotopy groups
Secondary homotopy groups supplement the structure of classical homotopy
groups. They yield a track functor on the track category of pointed spaces
compatible with fiber sequences, suspensions and loop spaces. They also yield
algebraic models of homotopy types with homotopy groups concentrated in two
consecutive dimensions.Comment: We added further commets and references to make the paper more easily
readabl
Optical Pumping of TeH+: Implications for the Search for Varying mp/me
Molecular overtone transitions provide optical frequency transitions
sensitive to variation in the proton-to-electron mass ratio (). However, robust molecular state preparation presents a challenge
critical for achieving high precision. Here, we characterize infrared and
optical-frequency broadband laser cooling schemes for TeH, a species with
multiple electronic transitions amenable to sustained laser control. Using rate
equations to simulate laser cooling population dynamics, we estimate the
fractional sensitivity to attainable using TeH. We find that laser
cooling of TeH can lead to significant improvements on current
variation limits
Evolution Operators for Linearly Polarized Two-Killing Cosmological Models
We give a general procedure to obtain non perturbative evolution operators in
closed form for quantized linearly polarized two Killing vector reductions of
general relativity with a cosmological interpretation. We study the
representation of these operators in Fock spaces and discuss in detail the
conditions leading to unitary evolutions.Comment: Accepted for publication in Physical Review
Effectively four-dimensional spacetimes emerging from d=5 Einstein-Gauss-Bonnet Gravity
Einstein-Gauss-Bonnet gravity in five-dimensional spacetime provides an
excellent example of a theory that, while including higher-order curvature
corrections to General Relativity, still shares many of its features, such as
second-order field equations for the metric. We focus on the largely unexplored
case where the coupling constants of the theory are such that no
constant-curvature solution is allowed, leaving open the question of what the
vacuum state should then be. We find that even a slight deviation from the
anti-de Sitter Chern-Simons theory, where the vacuum state is five-dimensional
AdS spacetime, leads to a complete symmetry breakdown, with the fifth dimension
either being compactified into a small circle or shrinking away exponentially
with time. A complete family of solutions, including duality relations among
them, is uncovered and shown to be unique within a certain class. This
dynamical dimensional reduction scenario seems particularly attractive as a
means for higher-dimensional theories to make contact with our four-dimensional
world.Comment: 9 pages, 4 figures. v2: New section on geometrical significance of
solutions. Final version for CQ
Rotating Dilaton Solutions in 2+1 Dimensions
We report a three parameter family of solutions for dilaton gravity in 2+1
dimensions with finite mass and finite angular momentum. These solutions are
obtained by a compactification of vacuum solutions in 3+1 dimensions with
cylindrical symmetry. One class of solutions corresponds to conical
singularities and the other leads to curvature singularities.Comment: Accepted to be published in Gen. Rel. Grav., added reference
Entanglement dynamics in presence of diversity under decohering environments
We study the evolution of entanglement of a pair of coupled, non-resonant
harmonic oscillators in contact with an environment. For both the cases of a
common bath and of two separate baths for each of the oscillators, a full
master equation is provided without rotating wave approximation. This allows us
to characterize the entanglement dynamics as a function of the diversity
between the oscillators frequencies and their mutual coupling. Also the
correlation between the occupation numbers is considered to explore the degree
of quantumness of the system. The singular effect of the resonance condition
(identical oscillators) and its relationship with the possibility of preserving
asymptotic entanglement are discussed. The importance of the bath's memory
properties is investigated by comparing Markovian and non-Markovian evolutions
The Pricing Behaviour of Firms in the Euro Area: New Survey Evidence
This study investigates the pricing behaviour of firms in the euro area on the basis of surveys conducted by nine Eurosystem national central banks. Overall, more than 11,000 firms participated in the survey. The results are very robust across countries. Firms operate in monopolistically competitive markets, where prices are mostly set following mark-up rules and where price discrimination is a common practice. Our evidence suggests that both time- and state-dependent pricing strategies are applied by firms in the euro area: around one-third of the companies follow mainly time-dependent pricing rules while two-thirds use pricing rules with some element of state-dependence. Although the majority of firms take into account a wide range of information, including past and expected economic developments, about one-third adopts a purely backward-looking behaviour. The pattern of results lends support to the recent wave of estimations of hybrid versions of the New Keynesian Phillips Curve. Price stickiness arises both at the stage when firms review their prices and again when they actually change prices. The most relevant factors underlying price rigidity are customer relationships – as expressed in the theories about explicit and implicit contracts – and thus, are mainly found at the price changing (second) stage of the price adjustment process. Finally, we provide evidence that firms adjust prices asymmetrically in response to shocks, depending on the direction of the adjustment and the source of the shock: while cost shocks have a greater impact when prices have to be raised than when they have to be reduced, reductions in demand are more likely to induce a price change than increases in demand.
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