13,065 research outputs found
Endogenous leadership in teams
In this paper we study the mechanics of “leading by example” in
teams. Leadership is beneficial for the entire team when agents are
conformists, i.e., dislike effort differentials. We also show how leadership
can arise endogenously and discuss what type of leader benefits
a team most
Phase transitions, entanglement and quantum noise interferometry in cold atoms
We show that entanglement monotones can characterize the pronounced
enhancement of entanglement at a quantum phase transition if they are sensitive
to long-range high order correlations. These monotones are found to develop a
sharp peak at the critical point and to exhibit universal scaling. We
demonstrate that similar features are shared by noise correlations and verify
that these experimentally accessible quantities indeed encode entanglement
information and probe separability.Comment: 4 pages 4 figure
Wavelet Analysis of Inhomogeneous Data with Application to the Cosmic Velocity Field
In this article we give an account of a method of smoothing spatial
inhomogeneous data sets by using wavelet reconstruction on a regular grid in an
auxilliary space onto which the original data is mapped. In a previous paper by
the present authors, we devised a method for inferring the velocity potential
from the radial component of the cosmic velocity field assuming an ideal
sampling. Unfortunately the sparseness of the real data as well as errors of
measurement require us to first smooth the velocity field as observed on a
3-dimensional support (i.e. the galaxy positions) inhomogeneously distributed
throughout the sampled volume. The wavelet formalism permits us to introduce a
minimal smoothing procedure that is characterized by the variation in size of
the smothing window function. Moreover the output smoothed radial velocity
field can be shown to correspond to a well defined theoretical quantity as long
as the spatial sampling support satisfies certain criteria. We argue also that
one should be very cautious when comparing the velocity potential derived from
such a smoothed radial component of the velocity field with related quantities
derived from other studies (e.g : of the density field).Comment: 19 pages, Latex file, figures are avaible under requests, published
in Inverse Problems, 11 (1995) 76
The Axion and the Goldstone Higgs
We consider the renormalizable -model, in which the
Higgs particle has a pseudo-Nambu-Goldstone boson character, and explore what
the minimal field extension required to implement the Peccei-Quinn symmetry
(PQ) is, within the partial compositeness scenario. It turns out that the
minimal model does not require the enlargement of the exotic fermionic sector,
but only the addition of a singlet scalar: it is sufficient that the exotic
fermions involved in partial compositeness and the singlet scalar become
charged under Peccei-Quinn transformations. We explore the phenomenological
predictions for photonic signals in axion searches for all models discussed.
Because of the constraints imposed on the exotic fermion sector by the Standard
Model fermion masses, the expected range of allowed axion-photon couplings
turns out to be generically narrowed with respect to that of standard invisible
axion models, impacting the experimental quest.Comment: 31 pages, 2 Figures. Description improved, results unchange
Deformed Superspace, N=1/2 Supersymmetry and (Non)Renormalization Theorems
We consider a deformed superspace in which the coordinates \theta do not
anticommute, but satisfy a Clifford algebra. We present results on the
properties of N=1/2 supersymmetric theories of chiral superfields in deformed
superspace, taking the Wess-Zumino model as the prototype. We prove new
(non)renormalization theorems: the F-term is radiatively corrected and becomes
indistinguishable from the D-term, while the Fbar-term is not renormalized.
Supersymmetric vacua are critical points of the antiholomorphic superpotential.
The vacuum energy is zero to all orders in perturbation theory. We illustrate
these results with several examples.Comment: 21 pages, 5 figures and one table; V2: references adde
INVESTMENT EFFECTS OF ENDOGENOUS AND EXOGENOUS DEPRECIATION: IMPROVED PASTURES IN URUGUAY
The depreciation rate for capital assets may have endogenous and exogenous components. Change in the exogenous component depends on technological change and/or environmental factors, shifts the production function, and independently affects profitability and investment. Change in the endogenous component does not. These hypotheses are tested using data on Uruguayan grass-legume pastures.Land Economics/Use,
Hanbury Brown-Twiss Interferometry for Fractional and Integer Mott Phases
Hanbury-Brown-Twiss interferometry (HBTI) is used to study integer and
fractionally filled Mott Insulator (MI) phases in period-2 optical
superlattices. In contrast to the quasimomentum distribution, this second order
interferometry pattern exhibits high contrast fringes in the it insulating
phases. Our detailed study of HBTI suggests that this interference pattern
signals the various superfluid-insulator transitions and therefore can be used
as a practical method to determine the phase diagram of the system. We find
that in the presence of a confining potential the insulating phases become
robust as they exist for a finite range of atom numbers. Furthermore, we show
that in the trapped case the HBTI interferogram signals the formation of the MI
domains and probes the shell structure of the system.Comment: 13 pages, 15 figure
Better age estimations using UV-optical colours: breaking the age-metallicity degeneracy
We demonstrate that the combination of GALEX UV photometry in the FUV (~1530
angstroms) and NUV (~2310 angstroms) passbands with optical photometry in the
standard U,B,V,R,I filters can efficiently break the age-metallicity
degeneracy. We estimate well-constrained ages, metallicities and their
associated errors for 42 GCs in M31, and show that the full set of
FUV,NUV,U,B,V,R,I photometry produces age estimates that are ~90 percent more
constrained and metallicity estimates that are ~60 percent more constrained
than those produced by using optical filters alone. The quality of the age
constraints is comparable or marginally better than those achieved using a
large number of spectrscopic indices.Comment: Published in MNRAS (2007), 381, L74 (doi:
10.1111/j.1745-3933.2007.00370.x
Model building in AdS/CMT: DC conductivity and Hall angle
Using the bottom-up approach in a holographic setting, we attempt to study
both the transport and thermodynamic properties of a generic system in 3+1
dimensional bulk spacetime. We show the exact 1/T and dependence of the
longitudinal conductivity and Hall angle, as seen experimentally in most
copper-oxide systems, which are believed to be close to quantum critical point.
This particular temperature dependence to conductivities are possible in two
different cases: (1) Background solutions with scale invariant and broken
rotational symmetry, (2) solutions with pseudo-scaling and unbroken rotational
symmetry but only at low density limit. Generically, the study of the transport
properties in a scale invariant background solution, using the probe brane
approach, at high density and at low temperature limit suggests us to consider
only metrics with two exponents. More precisely, the spatial part of the metric
components should not be same i.e., . In doing so, we have
generated the above mentioned behavior to conductivity with a very special
behavior to specific heat which at low temperature goes as: .
However, if we break the scaling symmetry of the background solution by
including a nontrivial dilaton, axion or both and keep the rotational symmetry
then also we can generate such a behavior to conductivity but only in the low
density regime. As far as we are aware, this particular temperature dependence
to both the conductivity and Hall angle is being shown for the first time using
holography.Comment: 1+40 pages; v2: Analysis of pseudo-scaling and rotational invariant
solutions are added; v3: Improved presentation; v4: Typos fixed and closer to
journal versio
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