A Class of Distal Functions on Semitopological Semigroups

The norm closure of the algebra generated by the set $\{n\mapsto {\lambda}^{n^k}:$ $\lambda\in{\mathbb {T}}$ and $k\in{\mathbb{N}}\}$ of functions on $({\mathbb {Z}}, +)$ was studied in \cite{S} (and was named as the Weyl algebra). In this paper, by a fruitful result of Namioka, this algebra is generalized for a general semitopological semigroup and, among other things, it is shown that the elements of the involved algebra are distal. In particular, we examine this algebra for $({\mathbb {Z}}, +)$ and (more generally) for the discrete (additive) group of any countable ring. Finally, our results are treated for a bicyclic semigroup.Comment: To appear in Methods Funct. Anal. Topolog

On Rigidity of 3d Asymptotic Symmetry Algebras

We study rigidity and stability of infinite dimensional algebras which are not subject to the Hochschild-Serre factorization theorem. In particular, we consider algebras appearing as asymptotic symmetries of three dimensional spacetimes, the BMS3, u(1) Kac-Moody and Virasoro algebras. We construct and classify the family of algebras which appear as deformations of BMS3, u(1) Kac-Moody and their central extensions by direct computations and also by cohomological analysis. The Virasoro algebra appears as a specific member in this family of rigid algebras; for this case stabilization procedure is inverse of the In\"on\"u-Wigner contraction relating Virasoro to BMS3 algebra. We comment on the physical meaning of deformation and stabilization of these algebras and relevance of the family of rigid algebras we obtainComment: 50 pages, one figure and two tables; v2: minor improvements, references adde

Nearing Extremal Intersecting Giants and New Decoupled Sectors in N = 4 SYM

We study near-horizon limits of near-extremal charged black hole solutions to five-dimensional $U(1)^3$ gauged supergravity carrying two charges, extending the recent work of Balasubramanian et.al. We show that there are two near-horizon decoupling limits for the near-extremal black holes, one corresponding to the near-BPS case and the other for the far from BPS case. Both of these limits are only defined on the 10d IIB uplift of the 5d black holes, resulting in a decoupled geometry with a six-dimensional part (conformal to) a rotating BTZ X $S^3$. We study various aspects of these decoupling limits both from the gravity side and the dual field theory side. For the latter we argue that there should be two different, but equivalent, dual gauge theory descriptions, one in terms of the 2d CFT's dual to the rotating BTZ and the other as certain large R-charge sectors of d=4,N =4 U(N) SYM theory. We discuss new BMN-type sectors of the N=4 SYM in the $N\to\infty$ limit in which the engineering dimensions scale as $N^{3/2}$ (for the near-BPS case) and as $N^2$ (for the far from BPS case).Comment: 44 pages, references added, minor change

Leptogenesis from Gravity Waves in Models of Inflation

We present a new mechanism for creating the observed cosmic matter-antimatter asymmetry which satisfies all three Sakharov conditions from one common thread, gravitational waves. We generate lepton number through the gravitational anomaly in the lepton number current. The source term comes from elliptically polarizated gravity waves that are produced during inflation if the inflaton field contains a CP-odd component. In simple inflationary scenarios, the generated matter asymmetry is very small. We describe some special conditions in which our mechanism can give a matter asymmetry of realistic size.Comment: 4 pages, RevTeX4.1 format; an error in computations correcte

Combining multi-criteria and space syntax analysis to assess a pedestrian network: the case of Oporto

This paper describes a GIS-based integrated approach to assess a pedestrian network by combining multi-criteria and space syntax. The analysis combines pedestrian attributes with street connectivity and both factors were evaluated by a group of experts. The approach was adopted in the city of Oporto. Results show that the city centre offers various conditions; however, overall they are poor for pedestrians. Moreover, the streets which scored best are not integrated into the network. The described approach can potentially be replicated in other cities in terms of improving the walkability and promoting sustainable urban mobility.This research was funded by the CIVITAS CAPITAL (Ref. No. MOVE/FP7/604778/CAPITAL) and by the Centre for Territory, Environment and Construction of the School of Engineering of University of Minho.info:eu-repo/semantics/publishedVersio

An Arena for Model Building in the Cohen-Glashow Very Special Relativity

The Cohen-Glashow Very Special Relativity (VSR) algebra [arXiv:hep-ph/0601236] is defined as the part of the Lorentz algebra which upon addition of CP or T invariance enhances to the full Lorentz group, plus the space-time translations. We show that noncommutative space-time, in particular noncommutative Moyal plane, with light-like noncommutativity provides a robust mathematical setting for quantum field theories which are VSR invariant and hence set the stage for building VSR invariant particle physics models. In our setting the VSR invariant theories are specified with a single deformation parameter, the noncommutativity scale \Lambda_{NC}. Preliminary analysis with the available data leads to \Lambda_{NC}\gtrsim 1-10 TeV. This note is prepared for the Proceedings of the G27 Mathematical Physics Conference, Yerevan 2008, and is based on arXiv:0806.3699[hep-th].Comment: Presented by M.M.Sh-J. in the G27 Mathematical Physics Conference, Yerevan 2008 as the 4th Weyl Prize Ceremony Tal

Accessibility and connectivity criteria for assessing walkability: an application in Qazvin, Iran

Distance is a recognized key determinant of walking. Pedestrians tend to choose the shortest route between two points. Shortest routes can be spatially described in terms of distances between two points or topologically described as the number of turns/directional changes between these points. This paper presents a methodology to evaluate the conditions provided by a street network to pedestrians, by using two space syntax measures. Accessibility was calculated through Angular Segment Analysis by Metric Distance (ASAMeD), a measure of street integration and choice strongly correlated with pedestrian movement pattern. Street Connectivity was calculated by using the space syntax measure of connectivity, which shows the direct connection of street nodes to each individual nodes. The streets criterion values of both approaches were normalized by using fuzzy logic linear functions. The method was applied in the city center of Qazvin, Iran. Results showed that the urban structure of Qazvin has a strong impact on the performance of the network. The old neighborhood centers widespread in the city center presented a high topological accessibility, while the most connected street are those streets crossing and surrounding the neighborhood areas. The method can be used to evaluate and improve pedestrian networks, as it can distinguish the most and least attractive streets according to the criteria used. These findings can be used to guide policies towards improving walkability and to create more walkable and sustainable cities.This research was funded by the JPI Urban Europe and FCT, grant number ENSUF/0004/2016

Effective temperatures in a simple model of non-equilibrium, non-Markovian dynamics

The concept of effective temperatures in nonequilibrium systems is studied within an exactly solvable model of non-Markovian diffusion. The system is coupled to two heat baths which are kept at different temperatures: one ('fast') bath associated with an uncorrelated Gaussian noise and a second ('slow') bath with an exponential memory kernel. Various definitions of effective temperatures proposed in the literature are evaluated and compared. The range of validity of these definitions is discussed. It is shown in particular, that the effective temperature defined from the fluctuation-dissipation relation mirrors the temperature of the slow bath in parameter regions corresponding to a separation of time scales. On the contrary, quasi-static and thermodynamic definitions of an effective temperature are found to display the temperature of the fast bath in most parameter regions