3,823 research outputs found
Exceptional thermodynamics: The equation of state of G(2) gauge theory
We present a lattice study of the equation of state in Yang-Mills theory
based on the exceptional G(2) gauge group. As is well-known, at zero
temperature this theory shares many qualitative features with real-world QCD,
including the absence of colored states in the spectrum and dynamical string
breaking at large distances. In agreement with previous works, we show that at
finite temperature this theory features a first-order deconfining phase
transition, whose nature can be studied by a semi-classical computation. We
also show that the equilibrium thermodynamic observables in the deconfined
phase bear striking quantitative similarities with those found in SU(N) gauge
theories: in particular, these quantities exhibit nearly perfect
proportionality to the number of gluon degrees of freedom, and the trace
anomaly reveals a characteristic quadratic dependence on the temperature, also
observed in SU(N) Yang-Mills theories (both in four and in three spacetime
dimensions). We compare our lattice data with analytical predictions from
effective models, and discuss their implications for the deconfinement
mechanism and high-temperature properties of strongly interacting,
non-supersymmetric gauge theories. Our results give strong evidence for the
conjecture that the thermal deconfining transition is governed by a universal
mechanism, common to all simple gauge groups.Comment: 1+36 pages, 8 figures; v2, 1+41 pages, 9 figures: scale setting
improved, discussion in section 1 slightly expanded, comments on the Monte
Carlo algorithm added, new references included, affiliation details for one
of the authors updated, minor misprints corrected: version published in the
journa
Multi-Sector and Multi-Panel Performance in 5G mmWave Cellular Networks
The next generation of cellular networks (5G) will exploit the mmWave
spectrum to increase the available capacity. Communication at such high
frequencies, however, suffers from high path loss and blockage, therefore
directional transmissions using antenna arrays and dense deployments are
needed. Thus, when evaluating the performance of mmWave mobile networks, it is
necessary to accurately model the complex channel, the directionality of the
transmission, but also the interplay that these elements can have with the
whole protocol stack, both in the radio access and in the higher layers. In
this paper, we improve the channel model abstraction of the mmWave module for
ns-3, by introducing the support of a more realistic antenna array model,
compliant with 3GPP NR requirements, and of multiple antenna arrays at the base
stations and mobile handsets. We then study the end-to-end performance of a
mmWave cellular network by varying the channel and antenna array
configurations, and show that increasing the number of antenna arrays and,
consequently, the number of sectors is beneficial for both throughput and
latency.Comment: to be published in 2018 IEEE Global Communications Conference:
Communication QoS, Reliability and Modeling (Globecom2018 CQRM), Abu Dhabi,
UAE, Dec 201
Hybrid Spectrum Sharing in mmWave Cellular Networks
While spectrum at millimeter wave (mmWave) frequencies is less scarce than at
traditional frequencies below 6 GHz, still it is not unlimited, in particular
if we consider the requirements from other services using the same band and the
need to license mmWave bands to multiple mobile operators. Therefore, an
efficient spectrum access scheme is critical to harvest the maximum benefit
from emerging mmWave technologies. In this paper, we introduce a new hybrid
spectrum access scheme for mmWave networks, where data is aggregated through
two mmWave carriers with different characteristics. In particular, we consider
the case of a hybrid spectrum scheme between a mmWave band with exclusive
access and a mmWave band where spectrum is pooled between multiple operators.
To the best of our knowledge, this is the first study proposing hybrid spectrum
access for mmWave networks and providing a quantitative assessment of its
benefits. Our results show that this approach provides major advantages with
respect to traditional fully licensed or fully unlicensed spectrum access
schemes, though further work is needed to achieve a more complete understanding
of both technical and non technical implications
Understanding Noise and Interference Regimes in 5G Millimeter-Wave Cellular Networks
With the severe spectrum shortage in conventional cellular bands,
millimeter-wave (mmWave) frequencies have been attracting growing attention for
next-generation micro- and picocellular wireless networks. A fundamental and
open question is whether mmWave cellular networks are likely to be noise- or
interference-limited. Identifying in which regime a network is operating is
critical for the design of MAC and physical-layer procedures and to provide
insights on how transmissions across cells should be coordinated to cope with
interference. This work uses the latest measurement-based statistical channel
models to accurately assess the Interference-to-Noise Ratio (INR) in a wide
range of deployment scenarios. In addition to cell density, we also study
antenna array size and antenna patterns, whose effects are critical in the
mmWave regime. The channel models also account for blockage, line-of-sight and
non-line-of-sight regimes as well as local scattering, that significantly
affect the level of spatial isolation
A Spectrum Sharing Solution for the Efficient Use of mmWave Bands in 5G Cellular Scenarios
Regulators all around the world have started identifying the portions of the
spectrum that will be used for the next generation of cellular networks. A band
in the mmWave spectrum will be exploited to increase the available capacity. In
response to the very high expected traffic demand, a sharing mechanism may make
it possible to use the spectrum more efficiently. In this work, moving within
the European and Italian regulatory conditions, we propose the use of Licensed
Spectrum Access (LSA) to coordinate sharing among cellular operators.
Additionally, we show some preliminary results on our research activities which
are focused on a dynamic spectrum sharing approach applied in simulated 5G
cellular scenarios.Comment: to be published in IEEE International Symposium on Dynamic Spectrum
Access Networks (IEEE DySPAN 2018), Seoul, Korea, Oct, 201
Who is the director of this movie? Automatic style recognition based on shot features
We show how low-level formal features, such as shot duration, meant as length
of camera takes, and shot scale, i.e. the distance between the camera and the
subject, are distinctive of a director's style in art movies. So far such
features were thought of not having enough varieties to become distinctive of
an author. However our investigation on the full filmographies of six different
authors (Scorsese, Godard, Tarr, Fellini, Antonioni, and Bergman) for a total
number of 120 movies analysed second by second, confirms that these
shot-related features do not appear as random patterns in movies from the same
director. For feature extraction we adopt methods based on both conventional
and deep learning techniques. Our findings suggest that feature sequential
patterns, i.e. how features evolve in time, are at least as important as the
related feature distributions. To the best of our knowledge this is the first
study dealing with automatic attribution of movie authorship, which opens up
interesting lines of cross-disciplinary research on the impact of style on the
aesthetic and emotional effects on the viewers
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