1,497 research outputs found
Orbital selective crossover and Mott transitions in an asymmetric Hubbard model of cold atoms in optical lattices
We study the asymmetric Hubbard model at half-filling as a generic model to
describe the physics of two species of repulsively interacting fermionic cold
atoms in optical lattices. We use Dynamical Mean Field Theory to obtain the
paramagnetic phase diagram of the model as function of temperature, interaction
strength and hopping asymmetry. A Mott transition with a region of two
coexistent solutions is found for all nonzero values of the hopping asymmetry.
At low temperatures the metallic phase is a heavy Fermi-liquid, qualitatively
analogous to the Fermi liquid state of the symmetric Hubbard model. Above a
coherence temperature, an orbital-selective crossover takes place, wherein one
fermionic species effectively localizes, and the resulting bad metallic state
resembles the non-Fermi liquid state of the Falicov-Kimball model. We compute
observables relevant to cold atom systems such as the double occupation, the
specific heat and entropy and characterize their behavior in the different
phases
Department of Electronics and Communication Engineering, Government College of Engineering, Bargur, Tamilnadu, India
Recently, wireless network technologies were designed for most of the applications. Congestion raised in the wireless network degrades the performance and reduces the throughput. Congestion-free network is quit essen- tial in the transport layer to prevent performance degradation in a wireless network. Game theory is a branch of applied mathematics and applied sciences that used in wireless network, political science, biology, computer science, philosophy and economics. e great challenges of wireless network are their congestion by various factors. E ective congestion-free alternate path routing is pretty essential to increase network performance. Stackelberg game theory model is currently employed as an e ective tool to design and formulate conges- tion issues in wireless networks. is work uses a Stackelberg game to design alternate path model to avoid congestion. In this game, leaders and followers are selected to select an alternate routing path. e correlated equilibrium is used in Stackelberg game for making better decision between non-cooperation and cooperation. Congestion was continuously monitored to increase the throughput in the network. Simulation results show that the proposed scheme could extensively improve the network performance by reducing congestion with the help of Stackelberg game and thereby enhance throughput
Weak coupling study of decoherence of a qubit in disordered magnetic environments
We study the decoherence of a qubit weakly coupled to frustrated spin baths.
We focus on spin-baths described by the classical Ising spin glass and the
quantum random transverse Ising model which are known to have complex
thermodynamic phase diagrams as a function of an external magnetic field and
temperature. Using a combination of numerical and analytical methods, we show
that for baths initally in thermal equilibrium, the resulting decoherence is
highly sensitive to the nature of the coupling to the environment and is
qualitatively different in different parts of the phase diagram. We find an
unexpected strong non-Markovian decay of the coherence when the random
transverse Ising model bath is prepared in an initial state characterized by a
finite temperature paramagnet. This is contrary to the usual case of
exponential decay (Markovian) expected for spin baths in finite temperature
paramagnetic phases, thereby illustrating the importance of the underlying
non-trivial dynamics of interacting quantum spinbaths.Comment: 12 pages, 18 figure
Phase diagram of the asymmetric Hubbard model and an entropic chromatographic method for cooling cold fermions in optical lattices
We study the phase diagram of the asymmetric Hubbard model (AHM), which is
characterized by different values of the hopping for the two spin projections
of a fermion or equivalently, two different orbitals. This model is expected to
provide a good description of a mass-imbalanced cold fermionic mixture in a 3D
optical lattice. We use the dynamical mean field theory to study various
physical properties of this system. In particular, we show how
orbital-selective physics, observed in multi-orbital strongly correlated
electron systems, can be realized in such a simple model. We find that the
density distribution is a good probe of this orbital selective crossover from a
Fermi liquid to a non-Fermi liquid state.
Below an ordering temperature , which is a function of both the
interaction and hopping asymmetry, the system exhibits staggered long range
orbital order. Apart from the special case of the symmetric limit, i.e.,
Hubbard model, where there is no hopping asymmetry, this orbital order is
accompanied by a true charge density wave order for all values of the hopping
asymmetry. We calculate the order parameters and various physical quantities
including the thermodynamics in both the ordered and disordered phases. We find
that the formation of the charge density wave is signaled by an abrupt increase
in the sublattice double occupancies. Finally, we propose a new method,
entropic chromatography, for cooling fermionic atoms in optical lattices, by
exploiting the properties of the AHM. To establish this cooling strategy on a
firmer basis, we also discuss the variations in temperature induced by the
adiabatic tuning of interactions and hopping parameters.Comment: 16 pages, 19 fig
Effective action approach to strongly correlated fermion systems
We construct a new functional for the single particle Green's function, which
is a variant of the standard Baym Kadanoff functional.
The stability of the stationary solutions to the new functional is directly
related to aspects of the irreducible particle hole interaction through the
Bethe Salpeter equation.
A startling aspect of this functional is that it allows a simple and rigorous
derivation of both the standard and extended dynamical mean field (DMFT)
equations as stationary conditions. Though the DMFT equations were formerly
obtained only in the limit of infinite lattice coordination, the new functional
described in the work, presents a way of directly extending DMFT to finite
dimensional systems, both on a lattice and in a continuum. Instabilities of the
stationary solution at the bifurcation point of the functional, signal the
appearance of a zero mode at the Mott transition which then couples t o
physical quantities resulting in divergences at the transition.Comment: 9 page
The Culture of Ancient Tamils as Shown in ‘Etthuthogai’ (Eight Anthologies) and ‘Pathinenkeelkanakku’ (18 Short Classics)
The development of human knowledge has undergone various evolutions according to the changes of time. From the day man began to think, his intellectual development began to function. A man went to different places in search of food and clothing, and when he stayed in one place, he came into contact with many people there and formed an ethnic group. Thus, human life became social. When man interacts with others and shares in their joys and sorrows and gives them comfort and relief, the mind-dependent behaviours emerge as traits. Traits regulate habits. If a man's actions embody the good qualities he has learned and the virtues taught by tradition become established, they are followed by others. Later, these practises are followed by many and blossom into culture. Culture refers to a person's unique characteristics, morals, behaviors, feelings based on beliefs, values, etc. found in life. Every culture has defined rules of conduct and plays a major role in determining the basic lifestyle of the people belonging to that culture. Culture is what the individual gives to society and what society conveys to the individual. There is no respectable life without character. Without such a culture, the movement of the world would not be better. Good manners are based on the virtues of love, purity, commonality, friendship, virtue, compassion, perspective, gratitude, altruism, tolerance, and neutrality. This article explores these qualities of ancient Tamils in ‘etthuthogai’ (Eight Anthologies) and ‘Pathinenkeelkanakku’ (18 short classics)
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