17,128 research outputs found
Stability of Mixed-Strategy-Based Iterative Logit Quantal Response Dynamics in Game Theory
Using the Logit quantal response form as the response function in each step,
the original definition of static quantal response equilibrium (QRE) is
extended into an iterative evolution process. QREs remain as the fixed points
of the dynamic process. However, depending on whether such fixed points are the
long-term solutions of the dynamic process, they can be classified into stable
(SQREs) and unstable (USQREs) equilibriums. This extension resembles the
extension from static Nash equilibriums (NEs) to evolutionary stable solutions
in the framework of evolutionary game theory. The relation between SQREs and
other solution concepts of games, including NEs and QREs, is discussed. Using
experimental data from other published papers, we perform a preliminary
comparison between SQREs, NEs, QREs and the observed behavioral outcomes of
those experiments. For certain games, we determine that SQREs have better
predictive power than QREs and NEs
Valley contrasting physics in graphene: magnetic moment and topological transport
We investigate physical properties that can be used to distinguish the valley
degree of freedom in systems where inversion symmetry is broken, using graphene
systems as examples. We show that the pseudospin associated with the valley
index of carriers has an intrinsic magnetic moment, in close analogy with the
Bohr magneton for the electron spin. There is also a valley dependent Berry
phase effect that can result in a valley contrasting Hall transport, with
carriers in different valleys turning into opposite directions transverse to an
in-plane electric field. These effects can be used to generate and detect
valley polarization by magnetic and electric means, forming the basis for the
so-called valley-tronics applications
Berry Phase Effects on Electronic Properties
Ever since its discovery, the Berry phase has permeated through all branches
of physics. Over the last three decades, it was gradually realized that the
Berry phase of the electronic wave function can have a profound effect on
material properties and is responsible for a spectrum of phenomena, such as
ferroelectricity, orbital magnetism, various (quantum/anomalous/spin) Hall
effects, and quantum charge pumping. This progress is summarized in a
pedagogical manner in this review. We start with a brief summary of necessary
background, followed by a detailed discussion of the Berry phase effect in a
variety of solid state applications. A common thread of the review is the
semiclassical formulation of electron dynamics, which is a versatile tool in
the study of electron dynamics in the presence of electromagnetic fields and
more general perturbations. Finally, we demonstrate a re-quantization method
that converts a semiclassical theory to an effective quantum theory. It is
clear that the Berry phase should be added as a basic ingredient to our
understanding of basic material properties.Comment: 48 pages, 16 figures, submitted to RM
Minimal field requirement in precessional magnetization switching
We investigate the minimal field strength in precessional magnetization
switching using the Landau-Lifshitz-Gilbert equation in under-critically damped
systems. It is shown that precessional switching occurs when localized
trajectories in phase space become unlocalized upon application of field
pulses. By studying the evolution of the phase space, we obtain the analytical
expression of the critical switching field in the limit of small damping for a
magnetic object with biaxial anisotropy. We also calculate the switching times
for the zero damping situation. We show that applying field along the medium
axis is good for both small field and fast switching times.Comment: 6 pages, 7 figure
Topological Classification of Crystalline Insulators with Point Group Symmetry
We show that in crystalline insulators point group symmetry alone gives rise
to a topological classification based on the quantization of electric
polarization. Using C3 rotational symmetry as an example, we first prove that
the polarization is quantized and can only take three inequivalent values.
Therefore, a Z3 topological classification exists. A concrete tight-binding
model is derived to demonstrate the Z3 topological phase transition. Using
first-principles calculations, we identify graphene on BN substrate as a
possible candidate to realize the Z3 topological states. To complete our
analysis we extend the classification of band structures to all 17
two-dimensional space groups. This work will contribute to a complete theory of
symmetry conserved topological phases and also elucidate topological properties
of graphene like systems
Patterns of variability in early life traits of a Mediterranean coastal fish
Spawning dates and pelagic larval duration (PLD) are early life traits (ELT) crucial for understanding life cycles, properly assessing patterns of connectivity and gathering indications about patchiness or homogeneity of larval pools. Considering that little attention has been paid to spatial variability in these traits, we investigated variability of ELT from the analysis of otolith microstructure in the common two-banded sea bream Diplodus vulgaris. In the southwestern Adriatic Sea, along ~200 km of coast (∼1° in latitude, 41.2° to 40.2°N), variability of ELT was assessed at multiple spatial scales. Overall, PLD (ranging from 25 to 61 d) and spawning dates (October 2009 to February 2010) showed significant variability at small scales (i.e. <6 km), but not at larger scales. These outcomes suggest patchiness of the larval pool at small spatial scales. Multiple causal processes underlying the observed variability are discussed, along with the need to properly consider spatial variability in ELT, for example when delineating patterns of connectivity. Copyright © 2013 Inter-Research
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