Chiral symmetry and bulk--boundary correspondence in periodically driven one-dimensional systems

Over the past few years, topological insulators have taken center stage in solid state physics. The desire to tune the topological invariants of the bulk and thus control the number of edge states has steered theorists and experimentalists towards periodically driving parameters of these systems. In such periodically driven setups, by varying the drive sequence the effective (Floquet) Hamiltonian can be engineered to be topological: then, the principle of bulk--boundary correspondence guarantees the existence of robust edge states. It has also been realized, however, that periodically driven systems can host edge states not predicted by the Floquet Hamiltonian. The exploration of such edge states, and the corresponding topological phases unique to periodically driven systems, has only recently begun. We contribute to this goal by identifying the bulk topological invariants of periodically driven one-dimensional lattice Hamiltonians with chiral symmetry. We find simple closed expressions for these invariants, as winding numbers of blocks of the unitary operator corresponding to a part of the time evolution, and ways to tune these invariants using sublattice shifts. We illustrate our ideas on the periodically driven Su-Schrieffer-Heeger model, which we map to a discrete time quantum walk, allowing theoretical results about either of these systems to be applied to the other. Our work helps interpret the results of recent simulations where a large number of Floquet Majorana fermions in periodically driven superconductors have been found, and of recent experiments on discrete time quantum walks

Scattering theory of topological phases in discrete-time quantum walks

One-dimensional discrete-time quantum walks show a rich spectrum of topological phases that have so far been exclusively analysed in momentum space. In this work we introduce an alternative approach to topology which is based on the scattering matrix of a quantum walk, adapting concepts from time-independent systems. For gapped quantum walks, topological invariants at quasienergies 0 and {\pi} probe directly the existence of protected boundary states, while quantum walks with a non-trivial quasienergy winding have a discrete number of perfectly transmistting unidirectional modes. Our classification provides a unified framework that includes all known types of topology in one dimensional discrete-time quantum walks and is very well suited for the analysis of finite size and disorder effects. We provide a simple scheme to directly measure the topological invariants in an optical quantum walk experiment.Comment: 12 pages. v2: minor correction

Total Quality Management (TQM) in Hungary

In up-to-date manufacturing, industrial quality has proven to be a key competitive advantage. An active market position and profits are associated with high quality products and services. Like the optical properties of a natural crystal, quality reflects the state of the whole industry, its marketing, research and development, design, production methods, human resources, logistics, costing and pricing, and capital background. All advancement in the productive and commercial capability of a company relates somehow to the quality of the delivered goods. The holistic approach to industrial quality appeals to industrial policymaking and company leadership; quality improvement converted into an authoritative management issue. Active commitment and program implantation by the people at the top usually decides the whole quality image of the company. The outstanding role that quality plays in industry, obliges IIASA to follow closely the developments in international strategies of quality promotion. We highly appreciate the enthusiastic response of Hungarian industry. It has been proved that an advanced knowledge of comprehensive quality management, accumulated in leading industrial countries, is clearly compatible with the socio-economic environment of the Hungarian Republic. Encouraging results achieved so far invite other countries, with at least comparable societal structure, to follow the Hungarian example. IIASA would be pleased to provide an intellectual background for such breakthroughs in the challenging area of total quality movement

Topology-driven nonlinear switching in Möbius discrete arrays

We examine the switching dynamics of discrete solitons propagating along two coupled discrete arrays which are twisted to form a Möbius strip. We analyze the potential of the topological switches by comparing the differences between the Möbius strip and untwisted discrete arrays. We employ the Ablowitz-Ladik (AL) model and reveal a nontrivial Berry phase associated with the monopole spectra in parameter space. We study the dynamical evolution of the AL soliton launched into one of the chains and observe its switching behavior. While in the untwisted discrete case, the soliton splits in nearly identical portions as the interchain coupling is increased, in the Möbius case and for weak coupling, we observe a well-defined "switching time" where the soliton switches completely from one chain to the other

The Herschel Stripe 82 Survey (HerS): maps and early catalog

We present the first set of maps and band-merged catalog from the Herschel Stripe 82 Survey (HerS). Observations at 250, 350, and 500μm were taken with the Spectral and Photometric Imaging Receiver instrument aboard the Herschel Space Observatory. HerS covers 79deg 2 along the SDSS Stripe 82 to an average depth of 13.0, 12.9, and 14.8mJybeam −1 (including confusion) at 250, 350, and 500μm, respectively. HerS was designed to measure correlations with external tracers of the dark matter density field—either point-like (i.e., galaxies selected from radio to X-ray) or extended (i.e., clusters and gravitational lensing)—in order to measure the bias and redshift distribution of intensities of infrared-emitting dusty star-forming galaxies and active galactic nuclei. By locating HerS in Stripe 82, we maximize the overlap with available and upcoming cosmological surveys. The band-merged catalog contains 3.3 × 10 4 sources detected at a significance of ?3σ (including confusion noise). The maps and catalog are available at http://www.astro.caltech.edu/hers/

On the Redshift Distribution and Physical Properties of ACT-Selected DSFGs

We present multi-wavelength detections of nine candidate gravitationally-lensed dusty starforming galaxies (DSFGs) selected at 218 GHz (1.4 mm) from the ACT equatorial survey. Among the brightest ACT sources, these represent the subset of the total ACT sample lying in Herschel SPIRE fields, and all nine of the 218 GHz detections were found to have bright Herschel counterparts. By fitting their spectral energy distributions (SEDs) with a modified blackbody model with power-law temperature distribution, we find the sample has a median redshift of 4.1 (+ 1.1, -10) (68 percent confidence interval), as expected for 218 GHz selection and an apparent total infrared luminosity of log 10(uL(sub IR)/solar luminosity) = 13.86(+0.33, -0.30), which suggests that they are either strongly lensed sources or unresolved collections of unlensed DSFGs. The effective apparent diameter of the sample is square root of mu d = 4.2 (+ 1.7, -1.0) kpc, further evidence of strong lensing of multiplicity, since the typical diameter of dusty star-forming galaxies is 1.0-2.5 kpc. We emphasize that the effective apparent diameter derives from SED modeling without the assumption of opticaly thin dust (as opposed to image morphology). We find that the sources have substantial optical depth (tau = (4.2+, -1.9) of dust around the peak in the modified blackbody spectrum (lambda obs is less than 500 micrometers), a result that is robust to model choice

A measurement of the millimetre emission and the Sunyaev-Zel'dovich effect associated with low-frequency radio sources

We present a statistical analysis of the millimetre-wavelength properties of 1.4GHz-selected sources and a detection of the Sunyaev–Zel’dovich (SZ) effect associated with the haloes that host them. We stack data at 148, 218 and 277GHz from the Atacama Cosmology Telescope at the positions of a large sample of radio AGN selected at 1.4GHz. The thermal SZ effect associated with the haloes that host the AGN is detected at the 5σ level through its spectral signature, representing a statistical detection of the SZ effect in some of the lowest mass haloes (average M 200 ≈ 10 13 M. h −1 70 ) studied to date. The relation between the SZ effect and mass (based on weak lensing measurements of radio galaxies) is consistent with that measured by Planck for local bright galaxies. In the context of galaxy evolution models, this study confirms that galaxies with radio AGN also typically support hot gaseous haloes. Adding Herschel observations allows us to show that the SZ signal is not significantly contaminated by dust emission. Finally, we analyse the contribution of radio sources to the angular power spectrum of the cosmic microwave background

A Measurement of the Millimeter Emission and the Sunyaev-zel'dovich Effect Associated with Low-frequency Radio Sources

We present a statistical analysis of the millimeter-wavelength properties of 1.4 GHz-selected sources and a detection of the Sunyaev-Zel'dovich Effect associated with the halos that host them. The Atacama Cosmology Telescope (ACT) has conducted a survey at 148 GHz, 218 GHz and 277 GHz along the celestial equator. Using samples of radio sources selected at 1.4 GHz from the Faint Images of the Radio Sky at Twenty-Centimeters (FIRST) Survey and the National Radio Astronomy Observatory Very Large Array Sky Survey (NVSS), we measure the stacked 148, 218 and 277 GHz flux densities for sources with 1.4 GHz flux densities ranging from 5 to 200 mJy. At these flux densities, the radio source population is dominated by active galactic nuclei (AGN), with both steep and at spectrum populations, which have combined radio-to-millimeter spectral indices ranging from 0.5 to 0.95, reecting the prevalence of steep spectrum sources at high flux densities and the presence of at spectrum sources at lower flux densities. The thermal Sunyaev-Zelapos;dovich (SZ) eect associated with the halos that host the AGN is detected at the 5 level through its spectral signature. When we compare the SZ eect with weak lensing measurements of radio galaxies, we find that the relation between the two is consistent with that measured by Planck for local bright galaxies. We present a detection of the SZ eect in some of the lowest mass halos (average M(sub 200) approx. equals 10(exp 13) solar M h(sup-1) (sub 70) ) studied to date. This detection is particularly important in the context of galaxy evolution models, as it confirms that galaxies with radio AGN also typically support hot gaseous halos. With Herschel* observations, we show that the SZ detection is not significantly contaminated by dusty galaxies or by dust associated with the AGN or galaxies hosting the AGN. We show that 5 mJy < S(sub 1:4) < 200 mJy radio sources contribute l(l +1)C(sub l)/(2 pi ) = 0:37+/- 0:03 micro K(exp 2) to the angular power spectrum at l = 3000 at 148 GHz, after accounting for the SZ effect associated with their host halos

A Measurement of the Millimeter Emission and the Sunyaev-Zel'dovich Effect Associated with Low-Frequency Radio Sources

We present a statistical analysis of the millimeter-wavelength properties of 1.4 GHz-selected sources and a detection of the Sunyaev-Zel'dovich effect associated with the halos that host them. We stack data at 148, 218 and 277 GHz from the Atacama Cosmology Telescope at the positions of a large sample of radio AGN selected at 1.4 GHz. The thermal Sunyaev-Zel'dovich (SZ) effect associated with the halos that host the AGN is detected at the 5 sigma level through its spectral signature, representing a statistical detection of the SZ effect in some of the lowest mass halos (average M(sub 200) approximately equals 10(sup 13) solar mass h(sub 70)(exp 1) ) studied to date. The relation between the SZ effect and mass (based on weak lensing measurements of radio galaxies) is consistent with that measured by Planck for local bright galaxies. In the context of galaxy evolution models, this study confirms that galaxies with radio AGN also typically support hot gaseous halos. Adding Herschel observations allows us to show that the SZ signal is not significantly contaminated by dust emission. Finally, we analyze the contribution of radio sources to the angular power spectrum of the cosmic microwave background