509 research outputs found
Combatting electoral traces: the Dutch tempest discussion and beyond
In the Dutch e-voting debate, the crucial issue leading to the abandonment of all electronic voting machines was compromising radiation, or tempest. Other countries, however, do not seem to be bothered by this risk. In this paper, we use actor-network theory to analyse the socio-technical origins of the Dutch tempest issue in e-voting, and its consequences for e-voting beyond the Netherlands. We introduce the term electoral traces to denote any physical, digital or social evidence of a voter's choices in an election. From this perspective, we provide guidelines for risk analysis as well as an overview of countermeasures
Economic analysis of deforestation in Mexico
This paper uses panel analyses to estimate relationships for agricultural planted area and beef cattle numbers at the state level in Mexico during the periods 1970-85, in order to determine the main factors affecting forest land conversion. Of the key policy variables, maize and fertilizer prices appear to be the main influences on the expansion of planted area, whereas beef prices and credit disbursement influence cattle numbers. Population growth also affects both livestock and agricultural activities, and income per capita is positively correlated with cattle expansion. These estimated relationships are used to examine the effects both of agricultural and livestock sectoral policy changes and of trade liberalization in Mexico resulting from the North American Free Trade Agreement (NAFTA). To avoid any unintended impacts of NAFTA on Deforestation, it may be necessary for Mexico to make complementary investments in Land improvements, especially for existing cultivation on rain fed land
Tuned MSSM Higgses as an inflaton
We consider the possibility that the vacuum energy density of the MSSM
(Minimal Supersymmetric Standard Model) flat direction condensate involving the
Higgses H_1 and H_2 is responsible for inflation. We also discuss how the
finely tuned Higgs potential at high vacuum expectation values can realize {\it
cosmologically} flat direction along which it can generate the observed density
perturbations, and after the end of inflation -- the coherent oscillations of
the Higgses reheat the universe with all the observed degrees of freedom,
without causing any problem for the electroweak phase transition.Comment: 6 pages, 5 figure
On three dimensional bosonization
We discuss Abelian and non-Abelian three dimensional bosonization within the
path-integral framework. We present a systematic approach leading to the
construction of the bosonic action which, together with the bosonization recipe
for fermion currents, describes the original fermion system in terms of vector
bosons.Comment: 15 pages, LaTe
Inflection point inflation: WMAP constraints and a solution to the fine-tuning problem
We consider observational constraints and fine-tuning issues in a
renormalizable model of inflection point inflation, with two independent
parameters. We derive constraints on the parameter space of this model arising
from the WMAP 7-year power spectrum. It has previously been shown that it is
possible to successfully embed this potential in the MSSM. Unfortunately, to do
this requires severe fine-tuning. We address this issue by introducing a hybrid
field to dynamically uplift the potential with a subsequent smooth phase
transition to end inflation at the necessary point. Large parameter regions
exist where this drastically reduces the fine-tuning required without ruining
the viability of the model. A side effect of this mechanism is that it
increases the width of the slow-roll region of the potential, thus also
alleviating the problem of the fine-tuning of initial conditions. The MSSM
embedding we study has been previously shown to be able to explain the
smallness of the neutrino masses. The hybrid transition does not spoil this
feature as there exist parameter regions where the fine-tuning parameter is as
large as and the neutrino masses remain small.Comment: 12 pages, 2 figures, JCAP style. Version accepted for publication in
JCAP. Modifications made to improve readability, as requested by the referee;
results and conclusions unchanged. References update
Inflection point inflation within supersymmetry
We propose to address the fine tuning problem of inflection point inflation
by the addition of extra vacuum energy that is present during inflation but
disappears afterwards. We show that in such a case, the required amount of fine
tuning is greatly reduced. We suggest that the extra vacuum energy can be
associated with an earlier phase transition and provide a simple model, based
on extending the SM gauge group to SU(3)_C \times SU(2)_L\times U(1)_Y\times
U(1)_{B-L}, where the Higgs field of U(1)_{B-L} is in a false vacuum during
inflation. In this case, there is virtually no fine tuning of the soft SUSY
breaking parameters of the flat direction which serves as the inflaton.
However, the absence of radiative corrections which would spoil the flatness of
the inflaton potential requires that the U(1)_{B-L} gauge coupling should be
small with g_{B-L}\leq 10^{-4}.Comment: 6 pages, 1 figur
The δN formula is the dynamical renormalization group
We derive the 'separate universe' method for the inflationary bispectrum,
beginning directly from a field-theory calculation. We work to tree-level in
quantum effects but to all orders in the slow-roll expansion, with masses
accommodated perturbatively. Our method provides a systematic basis to account
for novel sources of time-dependence in inflationary correlation functions, and
has immediate applications. First, we use our result to obtain the correct
matching prescription between the 'quantum' and 'classical' parts of the
separate universe computation. Second, we elaborate on the application of this
method in situations where its validity is not clear. As a by-product of our
calculation we give the leading slow-roll corrections to the three-point
function of field fluctuations on spatially flat hypersurfaces in a canonical,
multiple-field model.Comment: v1: 33 pages, plus appendix and references; 5 figures. v2:
typographical typos fixed, minor changes to the main text and abstract,
reference added; matches version published in JCA
From semiclassical transport to quantum Hall effect under low-field Landau quantization
The crossover from the semiclassical transport to quantum Hall effect is
studied by examining a two-dimensional electron system in an AlGaAs/GaAs
heterostructure. By probing the magneto-oscillations, it is shown that the
semiclassical Shubnikov-de Haas (SdH) formulation can be valid even when the
minima of the longitudinal resistivity approach zero. The extension of the
applicable range of the SdH theory could be due to the damping effects
resulting from disorder and temperature. Moreover, we observed plateau-plateau
transition like behavior with such an extension. From our study, it is
important to include the positive magnetoresistance to refine the SdH theory.Comment: 11 pages, 5 figure
Squeezed States in the de Sitter Vacuum
We discuss the treatment of squeezed states as excitations in the Euclidean
vacuum of de Sitter space. A comparison with the treatment of these states as
candidate no-particle states, or alpha-vacua, shows important differences
already in the free theory. At the interacting level alpha-vacua are
inconsistent, but squeezed state excitations seem perfectly acceptable. Indeed,
matrix elements can be renormalized in the excited states using precisely the
standard local counterterms of the Euclidean vacuum. Implications for
inflationary scenarios in cosmology are discussed.Comment: 15 pages, no figures. One new citation in version 3; no other change
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