3,126 research outputs found
Dynamics of Quantum Coherence and Quantum Fisher Information After Sudden Quench
The dynamics of relative entropy and -norm of coherence, as well as,
the Wigner-Yanase-skew and quantum Fisher information are studied for a
time-dependent coupled XY spin chain in presence of a time-dependent transverse
magnetic field. Independent of the initial state of the system and while the
relative entropy of coherence, -norm of coherence, and quantum Fisher
information are incapable, surprisingly, the dynamic Wigner-Yanase-skew
information can truly spotlight the equilibrium critical point. We also observe
that when the system is quenched to the critical point, these quantities show
suppressions and revivals. Moreover, the first suppression (revival) time
scales linearly with the system size and its scaling ratio is unique for all
quenches independent to the initial phase. This is the promised universality of
the first suppression (revival) time.Comment: 8 pages, 8 figures; to appear in Phys. Rev.
Some Quantitative Characterizations of Certain Symplectic Groups
Given a finite group , denote by the degree pattern of
and by the set of all order components of . Denote by (resp. ) the number of isomorphism classes of finite
groups satisfying conditions and (resp.
). A finite group is called OD-characterizable
(resp. OC-characterizable) if (resp. ). Let
be a symplectic group over binary field, for which is a
Mersenne prime. The aim of this article is to prove that
Disordered Kitaev chain with long-range pairing: Loschmidt echo revivals and dynamical phase transitions
We explore the dynamics of long-range Kitaev chain by varying pairing
interaction exponent, . It is well known that distinctive
characteristics on the nonequilibrium dynamics of a closed quantum system are
closely related to the equilibrium phase transitions. Specifically, the return
probability of the system to its initial state (Loschmidt echo), in the finite
size system, is expected to exhibit very nice periodicity after a sudden quench
to a quantum critical point. Where the periodicity of the revivals scales
inversely with the maximum of the group velocity. We show that, contrary to
expectations, the periodicity of the return probability breaks for a sudden
quench to the non-trivial quantum critical point. Further, We find that, the
periodicity of return probability scales inversely with the group velocity at
the gap closing point for a quench to the trivial critical point of truly
long-range pairing case, . In addition, analyzing the effect of
averaging quenched disorder shows that the revivals in the short range pairing
cases are more robust against disorder than that of the long rang pairing case.
We also study the effect of disorder on the non-analyticities of rate function
of the return probability which introduced as a witness of the dynamical phase
transition. We exhibit that, the non-analyticities in the rate function of
return probability are washed out in the presence of strong disorders.Comment: 13+ pages, 8 figures, new results adde
On the Unit Graph of a Noncommutative Ring
Let be a ring (not necessary commutative) with non-zero identity. The
unit graph of , denoted by , is a graph with elements of as its
vertices and two distinct vertices and are adjacent if and only if
is a unit element of . It was proved that if is a commutative ring
and \fm is a maximal ideal of such that |R/\fm|=2, then is a
complete bipartite graph if and only if (R, \fm) is a local ring. In this
paper we generalize this result by showing that if is a ring (not necessary
commutative), then is a complete -partite graph if and only if (R,
\fm) is a local ring and , for some or is a finite
field. Among other results we show that if is a left Artinian ring, and the clique number of is finite, then is a finite ring.Comment: 6 pages. To appear in Algebra Colloquiu
Quasiparticle interference in iron-based superconductors
We systematically calculate quasiparticle interference (QPI) signatures for
the whole phase diagram of iron-based superconductors. Impurities inherent in
the sample together with ordered phases lead to distinct features in the QPI
images that are believed to be measured in spectroscopic imaging-scanning
tunneling microscopy (SI-STM). In the spin-density wave phase the rotational
symmetry of the electronic structure is broken, signatures of which are also
seen in the coexistence regime with both superconducting and magnetic order. In
the superconducting regime we show how the different scattering behavior for
magnetic and non-magnetic impurities allows to verify the symmetry of
the order parameter. The effect of possible gap minima or nodes is discussed.Comment: 19 pages, 7 figure
Average energy efficiency contours with multiple decoding policies
This letter addresses energy-efficient design in multi-user, single-carrier uplink channels by employing multiple decoding policies. The comparison metric used in this study is based on average energy efficiency contours, where an optimal rate vector is obtained based on four system targets: Maximum energy efficiency, a trade-off between maximum energy efficiency and rate fairness, achieving energy efficiency target with maximum sum-rate and achieving energy efficiency target with fairness. The transmit power function is approximated using Taylor series expansion, with simulation results demonstrating the achievability of the optimal rate vector, and negligible performance difference in employing this approximation
Nilpotent maximal subgroups of GLn(D)
AbstractIn [S. Akbari, J. Algebra 217 (1999) 422–433] it has been conjectured that if D is a noncommutative division ring, then D∗ contains no nilpotent maximal subgroup. In connection with this conjecture we show that if GLn(D) contains a nilpotent maximal subgroup, say M, then M is abelian, provided D is infinite. This extends one of the main results appeared in [S. Akbari, J. Algebra 259 (2003) 201–225, Theorem 4]
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