45,124 research outputs found
Libor at crossroads: stochastic switching detection using information theory quantifiers
This paper studies the 28 time series of Libor rates, classified in seven
maturities and four currencies), during the last 14 years. The analysis was
performed using a novel technique in financial economics: the
Complexity-Entropy Causality Plane. This planar representation allows the
discrimination of different stochastic and chaotic regimes. Using a temporal
analysis based on moving windows, this paper unveals an abnormal movement of
Libor time series arround the period of the 2007 financial crisis. This
alteration in the stochastic dynamics of Libor is contemporary of what press
called "Libor scandal", i.e. the manipulation of interest rates carried out by
several prime banks. We argue that our methodology is suitable as a market
watch mechanism, as it makes visible the temporal redution in informational
efficiency of the market.Comment: 17 pages, 9 figures. arXiv admin note: text overlap with
arXiv:1508.04748, arXiv:1509.0021
The (in)visible hand in the Libor market: an Information Theory approach
This paper analyzes several interest rates time series from the United
Kingdom during the period 1999 to 2014. The analysis is carried out using a
pioneering statistical tool in the financial literature: the complexity-entropy
causality plane. This representation is able to classify different stochastic
and chaotic regimes in time series. We use sliding temporal windows to assess
changes in the intrinsic stochastic dynamics of the time series. Anomalous
behavior in the Libor is detected, especially around the time of the last
financial crisis, that could be consistent with data manipulation.Comment: PACS 89.65.Gh Econophysics; 74.40.De noise and chao
A permutation Information Theory tour through different interest rate maturities: the Libor case
This paper analyzes Libor interest rates for seven different maturities and
referred to operations in British Pounds, Euro, Swiss Francs and Japanese Yen,
during the period years 2001 to 2015. The analysis is performed by means of two
quantifiers derived from Information Theory: the permutation Shannon entropy
and the permutation Fisher information measure. An anomalous behavior in the
Libor is detected in all currencies except Euro during the years 2006--2012.
The stochastic switch is more severe in 1, 2 and 3 months maturities. Given the
special mechanism of Libor setting, we conjecture that the behavior could have
been produced by the manipulation that was uncovered by financial authorities.
We argue that our methodology is pertinent as a market overseeing instrument.Comment: arXiv admin note: text overlap with arXiv:1304.039
Wavelets Applied to CMB Maps: a Multiresolution Analysis for Denoising
Analysis and denoising of Cosmic Microwave Background (CMB) maps are
performed using wavelet multiresolution techniques. The method is tested on
maps with resolution resembling the
experimental one expected for future high resolution space observations.
Semianalytic formulae of the variance of wavelet coefficients are given for the
Haar and Mexican Hat wavelet bases. Results are presented for the standard Cold
Dark Matter (CDM) model. Denoising of simulated maps is carried out by removal
of wavelet coefficients dominated by instrumental noise. CMB maps with a
signal-to-noise, , are denoised with an error improvement factor
between 3 and 5. Moreover we have also tested how well the CMB temperature
power spectrum is recovered after denoising. We are able to reconstruct the
's up to with errors always below in cases with
.Comment: latex file 9 pages + 5 postscript figures + 1 gif figure (figure 6),
to be published in MNRA
Analytical Results for the Statistical Distribution Related to Memoryless Deterministic Tourist Walk: Dimensionality Effect and Mean Field Models
Consider a medium characterized by N points whose coordinates are randomly
generated by a uniform distribution along the edges of a unitary d-dimensional
hypercube. A walker leaves from each point of this disordered medium and moves
according to the deterministic rule to go to the nearest point which has not
been visited in the preceding \mu steps (deterministic tourist walk). Each
trajectory generated by this dynamics has an initial non-periodic part of t
steps (transient) and a final periodic part of p steps (attractor). The
neighborhood rank probabilities are parameterized by the normalized incomplete
beta function I_d = I_{1/4}[1/2,(d+1)/2]. The joint distribution
S_{\mu,d}^{(N)}(t,p) is relevant, and the marginal distributions previously
studied are particular cases. We show that, for the memory-less deterministic
tourist walk in the euclidean space, this distribution is:
S_{1,d}^{(\infty)}(t,p) = [\Gamma(1+I_d^{-1})
(t+I_d^{-1})/\Gamma(t+p+I_d^{-1})] \delta_{p,2}, where t=0,1,2,...,\infty,
\Gamma(z) is the gamma function and \delta_{i,j} is the Kronecker's delta. The
mean field models are random link model, which corresponds to d \to \infty, and
random map model which, even for \mu = 0, presents non-trivial cycle
distribution [S_{0,rm}^{(N)}(p) \propto p^{-1}]: S_{0,rm}^{(N)}(t,p) =
\Gamma(N)/\{\Gamma[N+1-(t+p)]N^{t+p}\}. The fundamental quantities are the
number of explored points n_e=t+p and I_d. Although the obtained distributions
are simple, they do not follow straightforwardly and they have been validated
by numerical experiments.Comment: 9 pages and 4 figure
On the Whitham hierarchy: dressing scheme, string equations and additional symmetrie
A new description of the universal Whitham hierarchy in terms of a
factorization problem in the Lie group of canonical transformations is
provided. This scheme allows us to give a natural description of dressing
transformations, string equations and additional symmetries for the Whitham
hierarchy. We show how to dress any given solution and prove that any solution
of the hierarchy may be undressed, and therefore comes from a factorization of
a canonical transformation. A particulary important function, related to the
-function, appears as a potential of the hierarchy. We introduce a class
of string equations which extends and contains previous classes of string
equations considered by Krichever and by Takasaki and Takebe. The scheme is
also applied for an convenient derivation of additional symmetries. Moreover,
new functional symmetries of the Zakharov extension of the Benney gas equations
are given and the action of additional symmetries over the potential in terms
of linear PDEs is characterized
On the Whitham hierarchy: dressing scheme, string equations and additional symmetrie
A new description of the universal Whitham hierarchy in terms of a
factorization problem in the Lie group of canonical transformations is
provided. This scheme allows us to give a natural description of dressing
transformations, string equations and additional symmetries for the Whitham
hierarchy. We show how to dress any given solution and prove that any solution
of the hierarchy may be undressed, and therefore comes from a factorization of
a canonical transformation. A particulary important function, related to the
-function, appears as a potential of the hierarchy. We introduce a class
of string equations which extends and contains previous classes of string
equations considered by Krichever and by Takasaki and Takebe. The scheme is
also applied for an convenient derivation of additional symmetries. Moreover,
new functional symmetries of the Zakharov extension of the Benney gas equations
are given and the action of additional symmetries over the potential in terms
of linear PDEs is characterized
An optimal estimator for the CMB-LSS angular power spectrum and its application to WMAP and NVSS data
We use a Quadratic Maximum Likelihood (QML) method to estimate the angular
power spectrum of the cross-correlation between cosmic microwave background and
large scale structure maps as well as their individual auto-spectra. We
describe our implementation of this method and demonstrate its accuracy on
simulated maps. We apply this optimal estimator to WMAP 7-year and NRAO VLA Sky
Survey (NVSS) data and explore the robustness of the angular power spectrum
estimates obtained by the QML method. With the correction of the declination
systematics in NVSS, we can safely use most of the information contained in
this survey. We then make use of the angular power spectrum estimates obtained
by the QML method to derive constraints on the dark energy critical density in
a flat CDM model by different likelihood prescriptions. When using
just the cross-correlation between WMAP 7 year and NVSS maps with 1.8
resolution, the best-fit model has a cosmological constant of approximatively
70% of the total energy density, disfavouring an Einstein-de Sitter Universe at
more than 2 CL (confidence level).Comment: 12 pages, 12 figure
Analysis of CMB maps with 2D wavelets
We consider the 2D wavelet transform with two scales to study sky maps of
temperature anisotropies in the cosmic microwave background radiation (CMB). We
apply this technique to simulated maps of small sky patches of size 12.8 \times
12.8 square degrees and 1.5' \times 1.5' pixels. The relation to the standard
approach, based on the cl's is established through the introduction of the
scalogram. We consider temperature fluctuations derived from standard, open and
flat-Lambda CDM models. We analyze CMB anisotropies maps plus uncorrelated
Gaussian noise (uniform and non-uniform) at idfferent S/N levels. We explore in
detail the denoising of such maps and compare the results with other techniques
already proposed in the literature. Wavelet methods provide a good
reconstruction of the image and power spectrum. Moreover, they are faster than
previously proposed methods.Comment: latex file 7 pages + 5 postscript files + 1 gif file; accepted for
publication in A&A
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