2,400 research outputs found
The (2+1)-d U(1) Quantum Link Model Masquerading as Deconfined Criticality
The -d U(1) quantum link model is a gauge theory, amenable to quantum
simulation, with a spontaneously broken SO(2) symmetry emerging at a quantum
phase transition. Its low-energy physics is described by a -d \RP(1)
effective field theory, perturbed by a dangerously irrelevant SO(2) breaking
operator, which prevents the interpretation of the emergent pseudo-Goldstone
boson as a dual photon. At the quantum phase transition, the model mimics some
features of deconfined quantum criticality, but remains linearly confining.
Deconfinement only sets in at high temperature.Comment: 4.5 pages, 6 figure
Crystalline Confinement
We show that exotic phases arise in generalized lattice gauge theories known
as quantum link models in which classical gauge fields are replaced by quantum
operators. While these quantum models with discrete variables have a
finite-dimensional Hilbert space per link, the continuous gauge symmetry is
still exact. An efficient cluster algorithm is used to study these exotic
phases. The -d system is confining at zero temperature with a
spontaneously broken translation symmetry. A crystalline phase exhibits
confinement via multi-stranded strings between charge-anti-charge pairs. A
phase transition between two distinct confined phases is weakly first order and
has an emergent spontaneously broken approximate global symmetry. The
low-energy physics is described by a -d effective field
theory, perturbed by a dangerously irrelevant breaking operator, which
prevents the interpretation of the emergent pseudo-Goldstone boson as a dual
photon. This model is an ideal candidate to be implemented in quantum
simulators to study phenomena that are not accessible using Monte Carlo
simulations such as the real-time evolution of the confining string and the
real-time dynamics of the pseudo-Goldstone boson.Comment: Proceedings of the 31st International Symposium on Lattice Field
Theory - LATTICE 201
Application Service Providing, Copyright, and Licensing, 25 J. Marshall J. Computer & Info. L. 79 (2007)
Application Service Providing ( ASP ), where a vendor hosts a software application on her server and grants customers access to the application over a network -- without the software application itself being installed on the user’s computer -- is used by many, e.g. in the form of Web based e-mail services, and grows ever more important. This article argues that although ASP mainly raises questions (i) that come up in the context of traditional use of computer programs; or (ii) that have been addressed in the context of online use of works other than software, ASP has significantly different copyright implications (which also affect software licensing). This is due to the technical differences between ASP and the traditional use of software – where the application is being installed on the user’s computer – and the differences between software and other works. Therefore, regarding new license agreements, the parties have to make sure that the license addresses issues of ASP and all the rights possibly affected by it, which may include rights other than those found in traditional software licensing. In the context of existing licenses, the question has to be raised whether they permit use of the licensed software in an ASP model. As an example of issues regarding already existing license agreements, this article will analyze the GNU General Public License in the light of ASP. The article further explains in which ASP-models the (end)user will need a (sub)license and in which cases she will not need a license. Examples of such agreements between the ASP-provider and the (end)user, agreements concerning Web based e-mail services will be examined
Two-dimensional Lattice Gauge Theories with Superconducting Quantum Circuits
A quantum simulator of U(1) lattice gauge theories can be implemented with
superconducting circuits. This allows the investigation of confined and
deconfined phases in quantum link models, and of valence bond solid and spin
liquid phases in quantum dimer models. Fractionalized confining strings and the
real-time dynamics of quantum phase transitions are accessible as well. Here we
show how state-of-the-art superconducting technology allows us to simulate
these phenomena in relatively small circuit lattices. By exploiting the strong
non-linear couplings between quantized excitations emerging when
superconducting qubits are coupled, we show how to engineer gauge invariant
Hamiltonians, including ring-exchange and four-body Ising interactions. We
demonstrate that, despite decoherence and disorder effects, minimal circuit
instances allow us to investigate properties such as the dynamics of electric
flux strings, signaling confinement in gauge invariant field theories. The
experimental realization of these models in larger superconducting circuits
could address open questions beyond current computational capability.Comment: Published versio
Geschlechterdisparität an der Spitze von Unternehmungen. Eine qualitative Untersuchung im Schweizer Bankensektor
Companies in Switzerland still face a scarcity of women in the executive committee, especially in CEO positions. Research has shown that there are various reasons for the very low ratio of female leaders in companies. Topics such as glass ceilings, glass cliffs, stereotypes, unconscious biases as well as gender in organizations in general have been studied in different international settings for many years. This dissertation aims to understand the gender disparity at the top of companies and focuses on Swiss banks by examining the life and career trajectories of female and male CEOs. To this end, the study uses the Bourdieu framework as a conceptual scheme and interpretative lens with its key constructs of habitus, capital and field and asks: What are the reasons for the acquisition of different capital in the various phases of life and what differences can be observed between women and men in this respect? How do gender-specific patterns of experience develop in the generation of capital, which is particularly relevant in a banking career? What significance does a specific habitus have in the process of CEO appointment in Swiss banks and how does a gender-specific habitus affect the number of women in CEO roles in Swiss banks?
This dissertation uses qualitive research methods. By questioning female and male CEOs of Swiss banks in semi-structured and open interviews, their life and career histories are examined and evaluated by means of qualitative content analysis. The key insights gained from this analysis are divided into three main areas. With regard to childhood capital accumulation, the results indicate that the intergenerational reproduction of gender differences in CEOs often originates in childhood experiences. The development of collective identities and social capital must be facilitated by taking into account gender differences in career and leadership development. Gender-specific and unequal patterns in the accumulation of capital play a role in the formation of the CEO habitus. Further research is needed to examine the life paths of CEOs in other industries in Switzerland as well as to study leadership development, particularly with regard to gender-specific experiences
Finite-Volume Energy Spectrum, Fractionalized Strings, and Low-Energy Effective Field Theory for the Quantum Dimer Model on the Square Lattice
We present detailed analytic calculations of finite-volume energy spectra,
mean field theory, as well as a systematic low-energy effective field theory
for the square lattice quantum dimer model. The analytic considerations explain
why a string connecting two external static charges in the confining columnar
phase fractionalizes into eight distinct strands with electric flux
. An emergent approximate spontaneously broken symmetry
gives rise to a pseudo-Goldstone boson. Remarkably, this soft phonon-like
excitation, which is massless at the Rokhsar-Kivelson (RK) point, exists far
beyond this point. The Goldstone physics is captured by a systematic low-energy
effective field theory. We determine its low-energy parameters by matching the
analytic effective field theory with exact diagonalization results and Monte
Carlo data. This confirms that the model exists in the columnar (and not in a
plaquette or mixed) phase all the way to the RK point.Comment: 35 pages, 16 figure
Recommended from our members
Heliothis dispersal and migration
A few of the many species of Heliothis (Lepidoptera, Noctuidae) are important crop pests in the Old and New Worlds. Among these, H.armigera, H.zea, H.virescens and H.punctigera are the best known. The former is a particularly destructive species of a wide range of crops cultivated in Africa, the Middle East and Asia, including several staple foods and important peasant farmer cash crops. As new cultivation techniques are introduced and more extensive areas of crops are grown, often on larger irrigation and Government development schemes, it appears that this pest is becoming increasingly important. There is a strong suspicion that H.armigera populations move locally between crops grown in sequence or intercropped and that probably more extensive migratory movement occurs, as has been demonstrated in the closely related species H. zea in North America. This has considerable implications for effective control of the pest on the crops of some of the least priviledged farmers of the Developing World and in some of the poorest countries. There are recorded instances of resistance to pesticides in the species. Clearly large scale movements could have an effect on dissemination of such resistance and affect the level of control exerted by local parasite and predator populations and hence the necessity for rapid control action to combat rapid population increases of the pest on both staple food and cash crops. The ability to forecast or warn of such incidents would assist in effective timing of control operations and maximise efficiency of any insecticidal input required. This bibliography consolidates much of the scattered literature on the migratory behaviour of Heliothis spp. and will help to identify gaps in the existing knowledge of this aspect of the ecology of the genus. It will hopefully assist in focussing attention on the necessity for work on H.armigera, which is of such great importance in Developing Countries. Work on migratory movement could lead to effective action both regionally and internationally to reduce possibilities of migration of damaging numbers of moths. It will certainly assist in increasing knowledge on the bionomics of one of the most damaging agricultural pest species in the Old World and be of benefit to some of the least advantaged farmers of the tropics
Avalanches and Dynamical Correlations in supercooled liquids
We identify the pattern of microscopic dynamical relaxation for a two
dimensional glass forming liquid. On short timescales, bursts of irreversible
particle motion, called cage jumps, aggregate into clusters. On larger time
scales, clusters aggregate both spatially and temporally into avalanches. This
propagation of mobility, or dynamic facilitation, takes place along the soft
regions of the systems, which have been identified by computing
isoconfigurational Debye-Waller maps. Our results characterize the way in which
dynamical heterogeneity evolves in moderately supercooled liquids and reveal
that it is astonishingly similar to the one found for dense glassy granular
media.Comment: 4 pages, 3 figure
Asymptotic diophantine approximation:the multiplicative case
Let and be irrational real numbers and 0<\F<1/30. We prove
a precise estimate for the number of positive integers that satisfy
\|q\alpha\|\cdot\|q\beta\|<\F. If we choose \F as a function of we get
asymptotics as gets large, provided \F Q grows quickly enough in terms of
the (multiplicative) Diophantine type of , e.g., if
is a counterexample to Littlewood's conjecture then we only
need that \F Q tends to infinity. Our result yields a new upper bound on sums
of reciprocals of products of fractional parts, and sheds some light on a
recent question of L\^{e} and Vaaler.Comment: To appear in Ramanujan Journa
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