3,611 research outputs found
Fermionic Networks: Modeling Adaptive Complex Networks with Fermionic Gases
We study the structure of Fermionic networks, i.e., a model of networks based
on the behavior of fermionic gases, and we analyze dynamical processes over
them. In this model, particle dynamics have been mapped to the domain of
networks, hence a parameter representing the temperature controls the evolution
of the system. In doing so, it is possible to generate adaptive networks, i.e.,
networks whose structure varies over time. As shown in previous works, networks
generated by quantum statistics can undergo critical phenomena as phase
transitions and, moreover, they can be considered as thermodynamic systems. In
this study, we analyze Fermionic networks and opinion dynamics processes over
them, framing this network model as a computational model useful to represent
complex and adaptive systems. Results highlight that a strong relation holds
between the gas temperature and the structure of the achieved networks.
Notably, both the degree distribution and the assortativity vary as the
temperature varies, hence we can state that fermionic networks behave as
adaptive networks. On the other hand, it is worth to highlight that we did not
find relation between outcomes of opinion dynamics processes and the gas
temperature. Therefore, although the latter plays a fundamental role in gas
dynamics, on the network domain its importance is related only to structural
properties of fermionic networks.Comment: 19 pages, 5 figure
Statistical mechanics of strings with Y-junctions
We investigate the Hagedorn transitions of string networks with Y-junctions
as may occur, for example, with (p,q) cosmic superstrings. In a simplified
model with three different types of string, the partition function reduces to
three generalised coupled XY models. We calculate the phase diagram and show
that, as the system is heated, the lightest strings first undergo the Hagedorn
transition despite the junctions. There is then a second, higher, critical
temperature above which infinite strings of all tensions, and junctions, exist.
Conversely, on cooling to low temperatures, only the lightest strings remain,
but they collapse into small loops
The Schwinger Model on the lattice in the Microcanonical Fermionic Average approach
The Microcanonical Fermionic Average method has been used so far in the
context of lattice models with phase transitions at finite coupling. To test
its applicability to Asymptotically Free theories, we have implemented it in
QED, \it i.e.\rm the Schwinger Model. We exploit the possibility, intrinsic
to this method, of studying the whole plane at negligible computer
cost, to follow constant physics trajectories and measure the limit
of the chiral condensate. We recover the continuum result within 3 decimal
places.Comment: TeX file, 7 pages + 3 figures in Postscrip
Spontaneous Symmetry Breaking and Phase Coexistence in Two-Color Networks
We have considered an equilibrium ensemble of large Erd\H{o}s-Renyi
topological random networks with fixed vertex degree and two types of vertices,
black and white, prepared randomly with the bond connection probability, .
The network energy is a sum of all unicolor triples (either black or white),
weighted with chemical potential of triples, . Minimizing the system
energy, we see for some positive formation of two predominantly unicolor
clusters, linked by a "string" of black-white bonds. We have
demonstrated that the system exhibits critical behavior manifested in emergence
of a wide plateau on the -curve, which is relevant to a spinodal
decomposition in 1st order phase transitions. In terms of a string theory, the
plateau formation can be interpreted as an entanglement between baby-universes
in 2D gravity. We have conjectured that observed classical phenomenon can be
considered as a toy model for the chiral condensate formation in quantum
chromodynamics.Comment: 9 pages, 4 figure
Fermi-Bose mixtures and BCS-BEC crossover in high-Tc superconductors
In this review article we consider theoretically and give experimental
support to the models of the Fermi-Bose mixtures and the BCS-BEC crossover
compared with the strong-coupling approach, which can serve as the cornerstones
on the way from high-temperature to room-temperature superconductivity in
pressurized metallic hydrides. We discuss some key theoretical ideas and
mechanisms proposed for unconventional superconductors (cuprates, pnictides,
chalcogenides, bismuthates, diborides, heavy-fermions, organics, bilayer
graphene, twisted graphene, oxide hetero-structures), superfluids and balanced
or imbalanced ultracold Fermi gases in magnetic traps. We build a bridge
between unconventional superconductors and recently discovered pressurized
hydrides superconductors H3S and LaH10 with the critical temperature close to
room temperature. We discuss systems with line of nodal Dirac points close to
the Fermi surface, superconducting shape resonances and hyperbolic
superconducting networks which are very important for the development of novel
topological superconductors, for the energetics, for the applications in
nano-electronics and quantum computations.Comment: 19 pages, 7 figure
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