56,428 research outputs found
Recursive Thick Modeling and the Choice of Monetary Policy in Mexico
By following the spirit in Favero and Milani (2005), we use recursive thick modeling to take into account model uncertainty for the choice of optimal monetary policy. We consider an open economy model and generate multiple models for only the aggregate demand and aggregate supply. Models are constructed by matching the rankings of aggregate demand and aggregate supply and adding other specifications for the rest of the variables. The main results show that recursive thick modeling with equal and different weights approximates the recent historical behavior of nominal interest rates in Mexico better than recursive thin modelingmodel uncertainty, optimal control, out-of-bag, thin modeling and thick modeling
Effective theories and constraints on new phyhsics
Anomalous moments of the top quark arises from one loop corrections to the
vertices and . We study these anomalous couplings
in different frameworks: effective theories, Standard Model and 2HDM. We use
available experimental results in order to get bounds on these anomalous
couplings.Comment: 8 pages, 2 figures, talk presented by R. Martinez at the X Mexican
School of Particles and Fields, Playa del Carmen, Mexico, 200
Sketch-based Influence Maximization and Computation: Scaling up with Guarantees
Propagation of contagion through networks is a fundamental process. It is
used to model the spread of information, influence, or a viral infection.
Diffusion patterns can be specified by a probabilistic model, such as
Independent Cascade (IC), or captured by a set of representative traces.
Basic computational problems in the study of diffusion are influence queries
(determining the potency of a specified seed set of nodes) and Influence
Maximization (identifying the most influential seed set of a given size).
Answering each influence query involves many edge traversals, and does not
scale when there are many queries on very large graphs. The gold standard for
Influence Maximization is the greedy algorithm, which iteratively adds to the
seed set a node maximizing the marginal gain in influence. Greedy has a
guaranteed approximation ratio of at least (1-1/e) and actually produces a
sequence of nodes, with each prefix having approximation guarantee with respect
to the same-size optimum. Since Greedy does not scale well beyond a few million
edges, for larger inputs one must currently use either heuristics or
alternative algorithms designed for a pre-specified small seed set size.
We develop a novel sketch-based design for influence computation. Our greedy
Sketch-based Influence Maximization (SKIM) algorithm scales to graphs with
billions of edges, with one to two orders of magnitude speedup over the best
greedy methods. It still has a guaranteed approximation ratio, and in practice
its quality nearly matches that of exact greedy. We also present influence
oracles, which use linear-time preprocessing to generate a small sketch for
each node, allowing the influence of any seed set to be quickly answered from
the sketches of its nodes.Comment: 10 pages, 5 figures. Appeared at the 23rd Conference on Information
and Knowledge Management (CIKM 2014) in Shanghai, Chin
A non-Markovian optical signature for detecting entanglement in coupled excitonic qubits
We identify an optical signature for detecting entanglement in experimental
nanostructure systems comprising coupled excitonic qubits. This signature owes
its strength to non-Markovian dynamical effects in the second-order temporal
coherence function of the emitted radiation. We calculate autocorrelation and
cross-correlation functions for both selective and collective light excitation,
and prove that the coherence properties of the emitted light do indeed carry
information about the entanglement of the initial multi-qubit state.
We also show that this signature can survive in the presence of a noisy
environment.Comment: 4 pages, 4 color figures. Minor changes. Accepted version to be
published in Europhysics Letter
The stellar-subhalo mass relation of satellite galaxies
We extend the abundance matching technique (AMT) to infer the
satellite-subhalo and central-halo mass relations (MRs) of galaxies, as well as
the corresponding satellite conditional mass functions (CMFs). We use the
observed galaxy stellar mass function (GSMF) decomposed into centrals and
satellites and the LCDM halo/subhalo mass functions as inputs. We explore the
effects of defining the subhalo mass at the time of accretion (m_acc) vs. at
the time of observation (m_obs). We test the standard assumption that centrals
and satellites follow the same MRs, showing that this assumption leads to
predictions in disagreement with observations, specially for m_obs. Instead,
when the satellite-subhalo MRs are constrained following our AMT, they are
always different from the central-halo MR: the smaller the stellar mass (Ms),
the less massive is the subhalo of satellites as compared to the halo of
centrals of the same Ms. On average, for Ms<2x10^11Msol, the dark mass of
satellites decreased by 60-65% with respect to their masses at accretion time.
The resulting MRs for both definitions of subhalo mass yield satellite CMFs in
agreement with observations. Also, when these MRs are used in a HOD model, the
predicted correlation functions agree with observations. We show that the use
of m_obs leads to less uncertain MRs than m_acc, and discuss implications of
the obtained satellite-subhalo MR. For example, we show that the tension
between abundance and dynamics of MW satellites in LCDM gives if the slope of
the GSMF faint-end slope upturns to -1.6.Comment: 13, pages, 4 figures. Accepted for publication in ApJ. Minor changes
to previous versio
Ultrafast optical signature of quantum superpositions in a nanostructure
We propose an unambiguous signature for detecting quantum superposition
states in a nanostructure, based on current ultrafast spectroscopy techniques.
The reliable generation of such superposition states via Hadamard-like quantum
gates is crucial for implementing solid-state based quantum information
schemes. The signature originates from a remarkably strong photon antibunching
effect which is enhanced by non-Markovian dynamics.Comment: 4 pages, 2 figures. Published in Phys. Rev. B (Rapid Communications
Controlled nucleation of topological defects in the stripe domain patterns of Lateral multilayers with Perpendicular Magnetic Anisotropy: competition between magnetostatic, exchange and misfit interactions
Magnetic lateral multilayers have been fabricated on weak perpendicular
magnetic anisotropy amorphous Nd-Co films in order to perform a systematic
study on the conditions for controlled nucleation of topological defects within
their magnetic stripe domain pattern. A lateral thickness modulation of period
is defined on the nanostructured samples that, in turn, induces a lateral
modulation of both magnetic stripe domain periods and average
in-plane magnetization component . Depending on lateral multilayer
period and in-plane applied field, thin and thick regions switch independently
during in-plane magnetization reversal and domain walls are created within the
in-plane magnetization configuration coupled to variable angle grain boundaries
and disclinations within the magnetic stripe domain patterns. This process is
mainly driven by the competition between rotatable anisotropy (that couples the
magnetic stripe pattern to in-plane magnetization) and in-plane shape
anisotropy induced by the periodic thickness modulation. However, as the
structural period becomes comparable to magnetic stripe period ,
the nucleation of topological defects at the interfaces between thin and thick
regions is hindered by a size effect and stripe domains in the different
thickness regions become strongly coupled.Comment: 10 pages, 7 figures, submitted to Physical Review
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