Noncommutative Field Theory

We review the generalization of field theory to space-time with noncommuting coordinates, starting with the basics and covering most of the active directions of research. Such theories are now known to emerge from limits of M theory and string theory, and to describe quantum Hall states. In the last few years they have been studied intensively, and many qualitatively new phenomena have been discovered, both on the classical and quantum level. To appear in Reviews of Modern Physics.Comment: Revtex, 56 pp, 6 figures. Final versio

Robust, Resilient Networked Communication in Challenged Environments

In challenged environments, digital communication infrastructure may be difficult or even impossible to access. This is especially true in rural and developing regions, as well as in any region during a time of political or environmental crisis. We advance the state of the art in wireless networking and security to design networks and applications that rapidly assess changing networking conditions to restore communication and provide local situational awareness. This dissertation examines new systems for responding to current and emerging needs for wireless networks. This work looks across the wireless ecosystem of widely deployed standards. We develop new tools to improve network assessment and to provide robust and reliable network communication. By incorporating new technological breakthroughs, such as the wide commercial success of Unmanned Aircraft Systems (UAS), we introduce novel methods and systems for existing wireless standards for these challenged networks. We assess how existing technologies and standards function in difficult environments: lacking end-end Internet connectivity, experiencing overload or other resource constraints, and operating in three dimensional space. Through this lens, we demonstrate how to optimize networks to serve marginalized communities outside of first world urban cities and make our networks resilient to natural and political crisis that threaten communication

Etnička zastupljenost ženskih autorica u časopisima za filozofiju prema regionalnoj pripadnosti i specijalizaciji

Using bibliographic metadata from 177 Philosophy Journals between 1950 and 2020, this article presents new data on the under- representation of women authors in philosophy journals across decades and across four different compounding factors. First, we examine how philosophy fits in comparison to other academic disciplines. Second, we consider how the regional academic context in which Philosophy Journals operate impacts on author gender proportions. Third, we consider how the regional specialization of a journal impacts on author gender proportions. Fourth, and perhaps most interestingly, we consider the impact of author ethnicity on gender representation, and we examine the breakdown of author ethnicity across Philosophy Journals between 1950 and 2020. To our knowledge, this is the first work to offer an estimate for author ethnicity and gender in philosophy publications using a large- scale data set. We find that women authors are underrepresented in Philosophy Journals across time, across disciplines, across the globe, and regardless of ethnicity.Koristeći bibliografske metapodatke iz 177 časopisa za filozofiju između 1950. i 2020. godine, ovaj članak predstavlja nove podatke o podzastupljenosti žena kao autorica u filozofskim časopisima tijekom desetljeća i četiri različita čimbenika. Prvo, istražujemo kako filozofija stoji u usporedbi s drugim akademskim disciplinama. Drugo, razmatramo kako regionalni akademski kontekst u kojem djeluju časopisi za filozofiju utječe na omjere rodova autora. Treće, razmatramo kako regionalna specijalizacija časopisa utječe na omjere rodova autora. Četvrto, i možda najzanimljivije, razmatramo utjecaj etničke pripadnosti autora na zastupljenost rodova, te proučavamo raspodjelu etničke pripadnosti autora u časopisima za filozofiju između 1950. i 2020. godine. Koliko nam je poznato, ovo je prvo istraživanje koje nudi procjenu etničke pripadnosti i roda autora u filozofskim publikacijama koristeći veliki skup podataka. Podaci pokazuju da su žene kao autorice podzastupljene u časopisima za filozofiju tijekom vremena, disciplina, širom svijeta i bez obzira na etničku pripadnost

On Four-Dimensional Compactifications of F-Theory

Branches of moduli space of F-theory in four dimensions are investigated. The transition between two branches is described as a 3-brane-instanton transition on a 7-brane. A dual heterotic picture of the transition is presented and the F-theory - heterotic theory map is given. The F-theory data - complex structure of the Calabi-Yau fourfold and the instanton bundle on the 7-brane is mapped to the heterotic bundle on the elliptic Calabi-Yau threefold CY_3. The full moduli space has a web structure which is also found in the moduli space of semi-stable bundles on $CY_3$. Matter content of the four-dimensional theory is discussed in both F-theory and heterotic theory descriptions.Comment: 40 pages, TeX, references added, minor changes in Section

ADHM and the 4d quantum Hall effect

Yang-Mills instantons are solitonic particles in d=4+1 dimensional gauge theories. We construct and analyse the quantum Hall states that arise when these particles are restricted to the lowest Landau level. We describe the ground state wavefunctions for both Abelian and non-Abelian quantum Hall states. Although our model is purely bosonic, we show that the excitations of this 4d quantum Hall state are governed by the Nekrasov partition function of a certain five dimensional supersymmetric gauge theory with Chern-Simons term. The partition function can also be interpreted as a variant of the Hilbert series of the instanton moduli space, counting holomorphic sections rather than holomorphic functions. It is known that the Hilbert series of the instanton moduli space can be rewritten using mirror symmetry of 3d gauge theories in terms of Coulomb branch variables. We generalise this approach to include the effect of a five dimensional Chern-Simons term. We demonstrate that the resulting Coulomb branch formula coincides with the corresponding Higgs branch Molien integral which, in turn, reproduces the standard formula for the Nekrasov partition function

Molecular Composition of Staufen2-Containing Ribonucleoproteins in Embryonic Rat Brain

Messenger ribonucleoprotein particles (mRNPs) are used to transport mRNAs along neuronal dendrites to their site of translation. Numerous mRNA-binding and regulatory proteins within mRNPs finely regulate the fate of bound-mRNAs. Their specific combination defines different types of mRNPs that in turn are related to specific synaptic functions. One of these mRNA-binding proteins, Staufen2 (Stau2), was shown to transport dendritic mRNAs along microtubules. Its knockdown expression in neurons was shown to change spine morphology and synaptic functions. To further understand the molecular mechanisms by which Stau2 modulates synaptic function in neurons, it is important to identify and characterize protein co-factors that regulate the fate of Stau2-containing mRNPs. To this end, a proteomic approach was used to identify co-immunoprecipitated proteins in Staufen2-containing mRNPs isolated from embryonic rat brains. The proteomic approach identified mRNA-binding proteins (PABPC1, hnRNP H1, YB1 and hsc70), proteins of the cytoskeleton (α- and β-tubulin) and RUFY3 a poorly characterized protein. While PABPC1 and YB1 associate with Stau2-containing mRNPs through RNAs, hsc70 is directly bound to Stau2 and this interaction is regulated by ATP. PABPC1 and YB1 proteins formed puncta in dendrites of embryonic rat hippocampal neurons. However, they poorly co-localized with Stau2 in the large dendritic complexes suggesting that they are rather components of Stau2-containing mRNA particles. All together, these results represent a further step in the characterization of Stau2-containing mRNPs in neurons and provide new tools to study and understand how Stau2-containing mRNPs are transported, translationally silenced during transport and/or locally expressed according to cell needs

Robust, Resilient Networked Communication in Challenged Environments

In challenged environments, digital communication infrastructure may be difficult or even impossible to access. This is especially true in rural and developing regions, as well as in any region during a time of political or environmental crisis. We advance the state of the art in wireless networking and security to design networks and applications that rapidly assess changing networking conditions to restore communication and provide local situational awareness. This dissertation examines new systems for responding to current and emerging needs for wireless networks. This work looks across the wireless ecosystem of widely deployed standards. We develop new tools to improve network assessment and to provide robust and reliable network communication. By incorporating new technological breakthroughs, such as the wide commercial success of Unmanned Aircraft Systems (UAS), we introduce novel methods and systems for existing wireless standards for these challenged networks. We assess how existing technologies and standards function in difficult environments: lacking end-end Internet connectivity, experiencing overload or other resource constraints, and operating in three dimensional space. Through this lens, we demonstrate how to optimize networks to serve marginalized communities outside of first world urban cities and make our networks resilient to natural and political crisis that threaten communication

Limits to Internet Freedoms: Being Heard in an Increasingly Authoritarian World

The Internet is a critical tool for communication and knowledge acquisition in societies across the globe. Unfortunately, its use has become a battlefield for governments, corporations, and individuals to censor speech and access to information. In this paper, we present research into the use of social media for free speech in Turkey, Mongolia, and Zambia as a basis for discussing the limits of Internet freedoms. We discuss the actors, adversaries, social and technological limits, as well as limitations of existing tools for the free exchange of ideas on-line. We conclude with a discussion of how design and development choices for technology can a.ect marginalized communities, as well as the ethical and technical considerations for developing tools and applications that support Internet freedoms