8,320 research outputs found
Bounded Concurrent Timestamp Systems Using Vector Clocks
Shared registers are basic objects used as communication mediums in
asynchronous concurrent computation. A concurrent timestamp system is a higher
typed communication object, and has been shown to be a powerful tool to solve
many concurrency control problems. It has turned out to be possible to
construct such higher typed objects from primitive lower typed ones. The next
step is to find efficient constructions. We propose a very efficient wait-free
construction of bounded concurrent timestamp systems from 1-writer multireader
registers. This finalizes, corrects, and extends, a preliminary bounded
multiwriter construction proposed by the second author in 1986. That work
partially initiated the current interest in wait-free concurrent objects, and
introduced a notion of discrete vector clocks in distributed algorithms.Comment: LaTeX source, 35 pages; To apper in: J. Assoc. Comp. Mac
Strange Half Metals and Mott Insulators in SYK Models
We study a dual flavor fermion model where each of the flavors form a
Sachdev-Ye-Kitaev (SYK) system with arbitrary and possibly distinct -body
interactions. The crucial new element is an arbitrary all-to-all -body
interaction between the two flavors. At high temperatures the model shows a
strange metal phase where both flavors are gapless, similar to the usual single
flavor SYK model. Upon reducing temperature, the coupled system undergoes phase
transitions to previously unseen phases - first, a strange half metal (SHM)
phase where one flavor remains a strange metal while the other is gapped, and,
second, a Mott insulating phase where both flavors are gapped. At a fixed low
temperature we obtain transitions between these phases by tuning the relative
fraction of sites for each flavor. We discuss the physics of these phases and
the nature of transitions between them. This work provides an example of an
instability of the strange metal with potential to provide new routes to study
strongly correlated systems through the rich physics contained in SYK like
models.Comment: 7 pages, 3 figure
Onset of Floquet Thermalisation
In presence of interactions, a closed, homogeneous (disorder-free) many-body
system is believed to generically heat up to an `infinite temperature' ensemble
when subjected to a periodic drive: in the spirit of the ergodicity hypothesis
underpinning statistical mechanics, this happens as no energy or other
conservation law prevents this. Here we present an interacting Ising chain
driven by a field of time-dependent strength, where such heating onsets only
below a threshold value of the drive amplitude, above which the system exhibits
non-ergodic behaviour. The onset appears at {\it strong, but not fast} driving.
This in particular puts it beyond the scope of high-frequency expansions. The
onset location shifts, but it is robustly present, across wide variations of
the model Hamiltonian such as driving frequency and protocol, as well as the
initial state. The portion of nonergodic states in the Floquet spectrum, while
thermodynamically subdominant, has a finite entropy. We find that the
magnetisation as an {\it emergent} conserved quantity underpinning the
freezing; indeed the freezing effect is readily observed, as initially
magnetised states remain partially frozen {\it up to infinite time}. This
result, which bears a family resemblance to the Kolmogorov-Arnold-Moser theorem
for classical dynamical systems, could be a valuable ingredient for extending
Floquet engineering to the interacting realm.Comment: 10 pages, including Supplemental Materia
Thermodynamics of the dissipative cosmic fluid and stability criteria
The work deals with the thermodynamical aspects of the cosmic substratum
which is dissipative in nature. For homogeneous and isotropic model of the
Universe this dissipative phenomenon is effective bulk viscous pressure in
nature and is related to the particle creation mechanism. Finally, the
stability criteria for the thermal equilibrium has been analyzed and are
presented in tabular form restricting the particle creation parameter or the
variation of the equation of state parameter with the volume.Comment: 9 page
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