50 research outputs found
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Epileptic spike-wave discharges in a spatially extended thalamocortical model
Non-perturbative dynamics of hot non-Abelian gauge fields: beyond leading log approximation
Many aspects of high-temperature gauge theories, such as the electroweak
baryon number violation rate, color conductivity, and the hard gluon damping
rate, have previously been understood only at leading logarithmic order (that
is, neglecting effects suppressed only by an inverse logarithm of the gauge
coupling). We discuss how to systematically go beyond leading logarithmic order
in the analysis of physical quantities. Specifically, we extend to
next-to-leading-log order (NLLO) the simple leading-log effective theory due to
Bodeker that describes non-perturbative color physics in hot non-Abelian
plasmas. A suitable scaling analysis is used to show that no new operators
enter the effective theory at next-to-leading-log order. However, a NLLO
calculation of the color conductivity is required, and we report the resulting
value. Our NLLO result for the color conductivity can be trivially combined
with previous numerical work by G. Moore to yield a NLLO result for the hot
electroweak baryon number violation rate.Comment: 20 pages, 1 figur
Meson Wave Functions From Holographic Qcd And The Role Of Infrared Renormalons In Proton-Proton Collisions
We calculate the contribution of the higher twist Feynman diagrams to the
large- inclusive pion production cross section in proton-proton collisions
in the case of the running and frozen coupling approaches within holographic
QCD. The structure of infrared renormalon singularities of the higher twist
subprocess cross section and it's resummed expression are found. We compare the
resummed higher twist cross sections with the ones obtained in the framework of
the frozen coupling approximation and leading twist cross section. We discuss
the phenomenological consequences of possible higher-twist contributions to the
pion production in proton-proton collisions within holographic QCD.Comment: 19 pages, 14 figures. arXiv admin note: substantial text overlap with
arXiv:1202.2632, arXiv:1107.1562, arXiv:1008.1646, arXiv:0803.019
Advances in perturbative thermal field theory
The progress of the last decade in perturbative quantum field theory at high
temperature and density made possible by the use of effective field theories
and hard-thermal/dense-loop resummations in ultrarelativistic gauge theories is
reviewed. The relevant methods are discussed in field theoretical models from
simple scalar theories to non-Abelian gauge theories including gravity. In the
simpler models, the aim is to give a pedagogical account of some of the
relevant problems and their resolution, while in the more complicated but also
more interesting models such as quantum chromodynamics, a summary of the
results obtained so far are given together with references to a few most recent
developments and open problems.Comment: 84 pages, 18 figues, review article submitted to Reports on Progress
in Physics; v2, v3: minor additions and corrections, more reference
Gauge-fixing parameter dependence of two-point gauge variant correlation functions
The gauge-fixing parameter dependence of two-point gauge variant
correlation functions is studied for QED and QCD. We show that, in three
Euclidean dimensions, or for four-dimensional thermal gauge theories, the usual
procedure of getting a general covariant gauge-fixing term by averaging over a
class of covariant gauge-fixing conditions leads to a nontrivial gauge-fixing
parameter dependence in gauge variant two-point correlation functions (e.g.
fermion propagators). This nontrivial gauge-fixing parameter dependence
modifies the large distance behavior of the two-point correlation functions by
introducing additional exponentially decaying factors. These factors are the
origin of the gauge dependence encountered in some perturbative evaluations of
the damping rates and the static chromoelectric screening length in a general
covariant gauge. To avoid this modification of the long distance behavior
introduced by performing the average over a class of covariant gauge-fixing
conditions, one can either choose a vanishing gauge-fixing parameter or apply
an unphysical infrared cutoff.Comment: 21 pages, RevTe
If I Were You: Perceptual Illusion of Body Swapping
The concept of an individual swapping his or her body with that of another person has captured the imagination of writers and artists for decades. Although this topic has not been the subject of investigation in science, it exemplifies the fundamental question of why we have an ongoing experience of being located inside our bodies. Here we report a perceptual illusion of body-swapping that addresses directly this issue. Manipulation of the visual perspective, in combination with the receipt of correlated multisensory information from the body was sufficient to trigger the illusion that another person's body or an artificial body was one's own. This effect was so strong that people could experience being in another person's body when facing their own body and shaking hands with it. Our results are of fundamental importance because they identify the perceptual processes that produce the feeling of ownership of one's body
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Preserved emotional awareness of pain in a patient with extensive bilateral damage to the insula, anterior cingulate, and amygdala
Functional neuroimaging investigations of pain have discovered a reliable pattern of activation within limbic regions of a putative "pain matrix" that has been theorized to reflect the affective dimension of pain. To test this theory, we evaluated the experience of pain in a rare neurological patient with extensive bilateral lesions encompassing core limbic structures of the pain matrix, including the insula, anterior cingulate, and amygdala. Despite widespread damage to these regions, the patient's expression and experience of pain was intact, and at times excessive in nature. This finding was consistent across multiple pain measures including self-report, facial expression, vocalization, withdrawal reaction, and autonomic response. These results challenge the notion of a "pain matrix" and provide direct evidence that the insula, anterior cingulate, and amygdala are not necessary for feeling the suffering inherent to pain. The patient's heightened degree of pain affect further suggests that these regions may be more important for the regulation of pain rather than providing the decisive substrate for pain's conscious experience
First results of the CAST-RADES haloscope search for axions at 34.67 ÎŒeV
We present results of the Relic Axion Dark-Matter Exploratory Setup (RADES), a detector which is part of the CERN Axion Solar Telescope (CAST), searching for axion dark matter in the 34.67ÎŒeV mass range. A radio frequency cavity consisting of 5 sub-cavities coupled by inductive irises took physics data inside the CAST dipole magnet for the first time using this filter-like haloscope geometry. An exclusion limit with a 95% credibility level on the axion-photon coupling constant of gaÎł & 4 Ă 10â13 GeVâ1 over a mass range of 34.6738ÎŒeV < ma < 34.6771ÎŒeV is set. This constitutes a significant improvement over the current strongest limit set by CAST at this mass and is at the same time one of the most sensitive direct searches for an axion dark matter candidate above the mass of 25ÎŒeV. The results also demonstrate the feasibility of exploring a wider mass range around the value probed by CAST-RADES in this work using similar coherent resonant cavitiesWe wish to thank our colleagues at CERN, in particular Marc Thiebert from the coating lab, as well as the whole team of the CERN Central Cryogenic Laboratory for their support and advice in speci c aspects of the project. We thank Arefe Abghari for her contributions as the project's summer student during 2018. This work has been funded by the Spanish Agencia Estatal de Investigacion (AEI) and Fondo Europeo de Desarrollo Regional (FEDER) under project FPA-2016-76978-C3-2-P and PID2019-108122GB-C33, and was supported by the CERN Doctoral Studentship programme. The research leading
to these results has received funding from the European Research Council and BD, JG and SAC acknowledge support through the European Research Council under grant ERC-2018-StG-802836 (AxScale project). BD also acknowledges fruitful discussions at MIAPP supported by DFG under EXC-2094 { 390783311. IGI acknowledges also support from the European Research Council (ERC) under grant ERC-2017-AdG-788781 (IAXO+ project). JR has been supported by the Ramon y Cajal Fellowship 2012-10597, the grant PGC2018-095328-B-I00(FEDER/Agencia estatal de investigaci on) and FSE-GA2017-2019-E12/7R (Gobierno de AragĂłn/FEDER) (MINECO/FEDER), the EU through the ITN \Elusives" H2020-MSCA-ITN-2015/674896 and the Deutsche Forschungsgemeinschaft under grant SFB-1258 as a Mercator Fellow. CPG was supported by PROMETEO II/2014/050 of Generalitat Valenciana, FPA2014-57816-P of MINECO and by the European Union's Horizon 2020 research and innovation program under the Marie Sklodowska-Curie grant agreements 690575 and 674896. AM is supported by the European Research Council under Grant No. 742104. Part of this work was performed under the auspices of the US Department of Energy by Lawrence Livermore National Laboratory under Contract No. DE-AC52-07NA27344
Gauge bosons at zero and finite temperature
Gauge theories of the Yang-Mills type are the single most important building
block of the standard model and beyond. Since Yang-Mills theories are gauge
theories their elementary particles, the gauge bosons, cannot be described
without fixing a gauge. Beyond perturbation theory, gauge-fixing in non-Abelian
gauge theories is obstructed by the Gribov-Singer ambiguity. The construction
and implementation of a method-independent gauge-fixing prescription to resolve
this ambiguity is the most important step to describe gauge bosons beyond
perturbation theory. Proposals for such a procedure, generalizing the
perturbative Landau gauge, are described here. Their implementation are
discussed for two example methods, lattice gauge theory and the quantum
equations of motion. The most direct access to the properties of the gauge
bosons is provided by their correlation functions. The corresponding two- and
three-point correlation functions are presented at all energy scales. These
give access to the properties of the gauge bosons, like their absence from the
asymptotic physical state space, the absence of an on-shell mass pole,
particle-like properties at high energies, and their running couplings.
Furthermore, auxiliary degrees of freedom are introduced during gauge-fixing,
and their properties are discussed as well. These results are presented for
two, three, and four dimensions, and for various gauge algebras. Finally, the
modifications of the properties of gauge bosons at finite temperature are
presented. Evidence is provided that these reflect the phase structure of
Yang-Mills theory. However, it is found that the phase transition is not
deconfining the gauge bosons, although the bulk thermodynamical behavior is of
a Stefan-Boltzmann type. The resolution of this apparent contradiction is also
presented. This resolution also provides an explicit and constructive solution
to the Linde problem.Comment: v2: 153 pages, 45 figures, revised, updated, and extended version
submitted on invitation to Physics Reports; v3: Intermediate update, 152
pages, 45 figures, minor errors corrected, reference list extended; v3 minor
typographical changes and corrections, added references, version to appear in
Physics Report