String order and adiabatic continuity of Haldane chains and band insulators

The ground state of spin-1 Haldane chains is characterized by the so-called string order. We show that the same hidden order is also present in ordinary one-dimensional band insulators. We construct a family of Hamiltonians which connects adiabatically band insulators to two topologically non-equivalent spin models, the Haldane chain and the antiferromagnetic spin-1/2 ladder. We observe that the localized spin-1/2 edge-state characteristic of spin-1 chains is smoothly connected to a surface-bound state of band insulators and its emergence is not related to any bulk phase transition. Furthermore, we show that the string order is absent in any dimensions higher than one.Comment: 6 pages, 7 figures. Appendix about charge string orders added. Version as publishe

Fragility of String Orders

One-dimensional gapped systems are often characterized by a 'hidden' non-local order parameter, the so-called string order. Due to the gap, thermodynamic properties are robust against a weak higher-dimensional coupling between such chains or ladders. To the contrary, we find that the string order is not stable and decays for arbitrary weak inter-chain or inter-ladder coupling. We investigate the vanishing of the order for three different systems: spin-one Haldane chains, band insulators, and the transverse-field Ising model. Using perturbation theory and bosonization, we show that the fragility of the string order arises from non-local commutation relations between the non-local order parameter and the perturbation.Comment: 7 pages, 3 figures. Published versio

Low-energy local density of states of the 1D Hubbard model

We examine the local density of states (DOS) at low energies numerically and analytically for the Hubbard model in one dimension. The eigenstates represent separate spin and charge excitations with a remarkably rich structure of the local DOS in space and energy. The results predict signatures of strongly correlated excitations in the tunneling probability along finite quantum wires, such as carbon nanotubes, atomic chains or semiconductor wires in scanning tunneling spectroscopy (STS) experiments. However, the detailed signatures can only be partly explained by standard Luttinger liquid theory. In particular, we find that the effective boundary exponent can be negative in finite wires, which leads to an increase of the local DOS near the edges in contrast to the established behavior in the thermodynamic limit.Comment: 6 pages, 4 figures, more information can be found at http://www.physik.uni-kl.de/eggert/papers/index.htm

Climate Change and the Mediterranean Southern Coasts

This chapter deals with climate change effects in the Mediterranean littoral of Morocco, which is one of the most vulnerable countries within the Mediterranean region, especially the low-lying areas located in the eastern, i.e., Nador and Saidia areas, and western parts, i.e., Tangier and Tetouan areas. The different aspects of climatic change characteristics and impacts are also analysed, including: sea level rise (SLR) trend in the Mediterranean littoral of Morocco; coastal erosion and flooding hazards; water management problems; and agricultural and tourist activities. It is established that appropriate vulnerability assessment and adaptation strategies to SLR and climate change are required at regional and national scale in Morocco, to improve the tools for correct coastal zone management

Coastal vulnerability in the Mediterranean sector between Fnideq and M’diq (North of Morocco)

This study assessed coastal vulnerability to erosion processes along a 24- km-long littoral with different levels of human occupation. An aerial photogram- metric flight and a Quickbird satellite image were used for mapping land uses and reconstructing coastal evolution from 1986 to 2003. Maximum erosion (- 2.48 myr−1) was recorded south of Marina Kabila port and maximum accretion (+2.25 myr−1) south of Marina Smir port. Erosion/accretion rates have been divided into five categories and land uses have been mapped and divided into three categories. Coastal vulnerability has been assessed by combining coastal trend with land-use categories: 10% of the littoral recorded “very high” vulner- ability, 29% recorded “high” vulnerability, and 61% of the investigated littoral presented “null” and “low” vulnerability. The “Imminent Collapse Zone”, i.e. the littoral zone threatened by imminent erosion, presented mean values of 10.34 m, with maximum and minimum values of 15.3 and 7.6 m, respectively. Several human structures and activities are located within the imminent collapse zone and consequently will be threatened by severe erosion in near future

Coastal sensitivity/vulnerability characterization and adaptation strategies: A review

Coastal area constitutes a vulnerable environment and requires special attention to preserve ecosystems and human activities therein. To this aim, many studies have been devoted both in past and recent years to analyzing the main factors affecting coastal vulnerability and susceptibility. Among the most used approaches, the Coastal Vulnerability Index (CVI) accounts for all relevant variables that characterize the coastal environment dealing with: (i) forcing actions (waves, tidal range, sea-level rise, etc.), (ii) morphological characteristics (geomorphology, foreshore slope, dune features, etc.), (iii) socio-economic, ecological and cultural aspects (tourism activities, natural habitats, etc.). Each variable is evaluated at each portion of the investigated coast, and associated with a vulnerability level which usually ranges from 1 (very low vulnerability), to 5 (very high vulnerability). Following a susceptibility/vulnerability analysis of a coastal stretch, specific strategies must be chosen and implemented to favor coastal resilience and adaptation, spanning from hard solutions (e.g., groins, breakwaters, etc.) to soft solutions (e.g., beach and dune nourishment projects), to the relocation option and the establishment of accommodation strategies (e.g., emergency preparedness)

Condensed Matter Theory of Dipolar Quantum Gases

Recent experimental breakthroughs in trapping, cooling and controlling ultracold gases of polar molecules, magnetic and Rydberg atoms have paved the way toward the investigation of highly tunable quantum systems, where anisotropic, long-range dipolar interactions play a prominent role at the many-body level. In this article we review recent theoretical studies concerning the physics of such systems. Starting from a general discussion on interaction design techniques and microscopic Hamiltonians, we provide a summary of recent work focused on many-body properties of dipolar systems, including: weakly interacting Bose gases, weakly interacting Fermi gases, multilayer systems, strongly interacting dipolar gases and dipolar gases in 1D and quasi-1D geometries. Within each of these topics, purely dipolar effects and connections with experimental realizations are emphasized.Comment: Review article; submitted 09/06/2011. 158 pages, 52 figures. This document is the unedited author's version of a Submitted Work that was subsequently accepted for publication in Chemical Reviews, copyright American Chemical Society after peer review. To access the final edited and published work, a link will be provided soo

The Sector Analysis as a Coastal Management Tool for Sustainable Tourism Development on the Mediterranean Coast of Morocco

Beaches are ecologically valuable ecosystems and sites that attract many tourists from all over the world, therefore, knowledge of their environmental conditions to establish sound management strategies is of extreme relevance. This study aims to assess and classify 50 beaches through an innovative coastal management approach called “Sector Analysis”, which integrates Litter grading, the coastal scenic quality and beach typology in order to classify sites into one of three sectors: Green (high value sites), Red (low value sites) and Yellow (sites with contradictory values). Litter Grade makes it possible to classify a site according to the quantity of litter using four grades from “A” (low) to “D” (high amount). The Coastal Scenic Evaluation System (CSES) allows to classify sites into five classes, ranging from extremely attractive natural sites (Class I) to unattractive degraded and urbanized sites (Class V). This innovative methodology for sustainable coastal area management can be easily applied to any beach in the world. The results on Litter Grade and CSES considered in this paper were obtained from previous studies and used to obtain the Sector Analysis that showed only 8 sites (16%) are in the Green sector, 18 sites (36%) in the Red sector and 24 sites (48%) in the Yellow sector. The significant percentage of sites in the Red sector (one third of the sites studied) clearly indicates the degradation that the Moroccan Mediterranean coast has undergone due to considerable anthropogenic activities and the lack of adequate coastal management programs. In this study, various management interventions were proposed to conserve and improve the aesthetic quality of beaches and reduce the impact and presence of litter in the coastal areas

Abundance and distribution of microplastics on sandy beaches of the eastern Moroccan Mediterranean coast

Microplastics (MPs) were investigated at 19 sandy beaches along the eastern Mediterranean Moroccan coast. Sediment samples (5 mm–63 μ m) were analyzed to identify MPs abundance, size, shape, color and nature. MPs concentration ranged from 40 ± 7.4 to 230 ± 48.6 MPs kg 1 ; fibrous MPs were the most abundant (74.72 %), followed by fragments (20.26 %), films (3.27 %), pellets (1.42 %) and foams (0.33 %). Large MPs (1–5 mm) accounted for 58 %, while small (< 1 mm) for 42 %. The 1–2 mm fraction of sediments presented the greatest amounts (30.67 %) of MPs. Transparent (50 %) and blue (17 %) were most common colors and most of particles were angular and irregularly shaped. Fourier Transform Infrared Spectroscopy (FTIR) analysis showed that PE (Polyethylene), PS (Polystyrene) and PP (Polypropylene) and PVC (Polyvinyl chloride) were the most common polymers. These findings revealed a moderate level of microplastic pollution along the beaches of the eastern Moroccan Mediterranean coast

Coastal Scenic Quality Assessment of Moroccan Mediterranean Beaches: A Tool for Proper Management

This paper focuses on the study of landscape quality of Moroccan Mediterranean coastal areas, with a view to distinguishing exceptional beaches with high scenic value. The main characteristics of 50 beaches along the studied coast were assessed using a coastal scenic evaluation system based on a set of 26 selected parameters, including physical (18) and human (8) parameters. Each parameter was examined via a five-point rating scale, ranging from presence/absence or poor quality (1) to excellent quality (5). A decision index (D) is afterward obtained and used to classify sites into five classes: Class I: D >= 0.85, which included 9 sites (18%); Class II: 0.85 > D >= 0.65, 10 sites (20%); Class III: 0.65 > D >= 0.40, 8 sites (16%); Class IV: 0.40 > D >= 0.00, 16 sites (32%); and Class V: D < 0.00, 7 sites (14%). The sites of Belyounech 2, Maresdar, El Hwad, and Dalya are the best examples of Class I and represent extremely attractive coastal landscapes. The sites of Ghandouri, Tangier Municipal, M'Diq, Martil, and Tangier Malabata are examples of degraded urban sites that are very unattractive due to high human pressures. Management efforts in Moroccan coastal landscapes can strengthen the control of human activities and improve the scenic value of the sites. Class II beaches, such as Mrisat, Souani, Taourirt, and Sfiha, could improve and upgrade to Class I through litter cleaning and a regular maintenance program. Using the same principle, Class III sites, such as Sidi Amer O Moussa and Sidi Driss, could improve and upgrade to Class II. Indeed, litter and sewage appear as the main factors of degradation of Moroccan coasts, and many excellent beaches are strongly affected by them. This should be a wakeup call to the Moroccan authorities to take urgent and appropriate management measures