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String theory

Zhe Wang, Jianda Wu, Wang Yang, Anup Kumar Bera, Dmytro Kamenskyi, A T M Nazmul Islam, Shenglong Xu, Joseph Matthew Law, Bella Lake, Congjun Wu, Alois Loidl
Almost a century ago, string states-complex bound states of magnetic excitations-were predicted to exist in one-dimensional quantum magnets. However, despite many theoretical studies, the experimental realization and identification of string states in a condensed-matter system have yet to be achieved. Here we use high-resolution terahertz spectroscopy to resolve string states in the antiferromagnetic Heisenberg-Ising chain SrCo2V2O8 in strong longitudinal magnetic fields. In the field-induced quantum-critical regime, we identify strings and fractional magnetic excitations that are accurately described by the Bethe ansatz...
February 7, 2018: Nature
R R Gazizulin, O Maillet, X Zhou, A Maldonado Cid, O Bourgeois, E Collin
We report on experiments performed within the Knudsen boundary layer of a low-pressure gas. The noninvasive probe we use is a suspended nanoelectromechanical string, which interacts with ^{4}He gas at cryogenic temperatures. When the pressure P is decreased, a reduction of the damping force below molecular friction ∝P had been first reported in Phys. Rev. Lett. 113, 136101 (2014)PRLTAO0031-900710.1103/PhysRevLett.113.136101 and never reproduced since. We demonstrate that this effect is independent of geometry, but dependent on temperature...
January 19, 2018: Physical Review Letters
Marko Tomislav Cvitas
The ring-polymer instanton (RPI) method is an efficient technique for calculating approximate tunneling splittings in high-dimensional molecular systems. In the RPI method, tunneling splitting is evaluated from the properties of the minimum action path (MAP) connecting the symmetric wells, whereby the extensive sampling of the full potential energy surface of the exact quantum-dynamics methods is avoided. Nevertheless, the search for the MAP is usually the most time-consuming step in the standard numerical procedures...
January 23, 2018: Journal of Chemical Theory and Computation
M Ruiz-Garcia, L L Bonilla, A Prados
We analyze a one-dimensional spin-string model, in which string oscillators are linearly coupled to their two nearest neighbors and to Ising spins representing internal degrees of freedom. String-spin coupling induces a long-range ferromagnetic interaction among spins that competes with a spin-spin antiferromagnetic coupling. As a consequence, the complex phase diagram of the system exhibits different flat rippled and buckled states, with first or second order transition lines between states. This complexity translates to the two-dimensional version of the model, whose numerical solution has been recently used to explain qualitatively the rippled to buckled transition observed in scanning tunneling microscopy experiments with suspended graphene sheets...
December 2017: Physical Review. E
Fabian Maucher, Paul Sutcliffe
In this paper, we present extensive numerical simulations of an excitable medium to study the long-term dynamics of knotted vortex strings for all torus knots up to crossing number 11. We demonstrate that FitzHugh-Nagumo evolution preserves the knot topology for all the examples presented, thereby providing a field theory approach to the study of knots. Furthermore, the evolution yields a well-defined minimal length for each knot that is comparable to the ropelength of ideal knots. We highlight the role of the medium boundary in stabilizing the length of the knot and discuss the implications beyond torus knots...
July 2017: Physical Review. E
Xinlu Zhou, Kongshuang Zhao
A dielectric spectroscopy study on a polyelectrolyte in aqueous solutions, which contains hydrophobic groups in part of the side chains poly(acrylic acid)-graft-poly(ethylene oxide)-graft-dodecyl (PAA-g-PEO-g-dodecyl) is reported. A refined double layer polarization model was proposed to analyze the double dielectric relaxations in the dielectric spectra. Various electrical and structural parameters of the copolymers were obtained. Besides the crossover concentration, another turning point around 4 mg mL-1 was identified through the analysis of all the dielectrical parameters including dielectric increment, relaxation time and correlation length...
January 18, 2018: Soft Matter
Isak Buhl-Mortensen, Marius de Leeuw, Asger C Ipsen, Charlotte Kristjansen, Matthias Wilhelm
We take the first step in extending the integrability approach to one-point functions in AdS/dCFT to higher loop orders. More precisely, we argue that the formula encoding all tree-level one-point functions of SU(2) operators in the defect version of N=4 supersymmetric Yang-Mills theory, dual to the D5-D3 probe-brane system with flux, has a natural asymptotic generalization to higher loop orders. The asymptotic formula correctly encodes the information about the one-loop correction to the one-point functions of nonprotected operators once dressed by a simple flux-dependent factor, as we demonstrate by an explicit computation involving a novel object denoted as an amputated matrix product state...
December 29, 2017: Physical Review Letters
Jigneshkumar Dahyabhai Prajapati, Carlos José Fernández Solano, Mathias Winterhalter, Ulrich Kleinekathöfer
In Gram-negative bacteria, the lack or quenching of antibiotics translocation across the outer membrane is one of the main factors for acquiring antibiotic resistance. An atomic level comprehension of the key features governing the transport of drugs by outer membrane protein channels will be very helpful in developing the next generation of antibiotics. In a previous study [J. D. Prajapati et al, J. Chem. Theory Comput. 2017, 13, 4553--4566], we characterized the diffusion pathway of the ciprofloxacin molecule through the outer membrane porin OmpC of E...
January 6, 2018: Journal of Physical Chemistry. B
Ivan De Martino, Tom Broadhurst, S-H Henry Tye, Tzihong Chiueh, Hsi-Yu Schive, Ruth Lazkoz
Light axionic dark matter, motivated by string theory, is increasingly favored for the "no weakly interacting massive particle era". Galaxy formation is suppressed below a Jeans scale of ≃10^{8}  M_{⊙} by setting the axion mass to m_{B}∼10^{-22}  eV, and the large dark cores of dwarf galaxies are explained as solitons on the de Broglie scale. This is persuasive, but detection of the inherent scalar field oscillation at the Compton frequency ω_{B}=(2.5  months)^{-1}(m_{B}/10^{-22}  eV) would be definitive...
December 1, 2017: Physical Review Letters
Vassiliy Lubchenko, Peter G Wolynes
Apart from not having crystallized, supercooled liquids can be considered as being properly equilibrated and thus can be described by a few thermodynamic control variables. In contrast, glasses and other amorphous solids can be arbitrarily far away from equilibrium and require a description of the history of the conditions under which they formed. In this paper we describe how the locality of interactions intrinsic to finite-dimensional systems affects the stability of amorphous solids far off equilibrium. Our analysis encompasses both structural glasses formed by cooling and colloidal assemblies formed by compression...
January 9, 2018: Journal of Physical Chemistry. B
Fei Yuan, WenCong Lu
Lung cancer is a serious disease that threatens an affected individual's life. Its pathogenesis has not yet to be fully described, thereby impeding the development of effective treatments and preventive measures. "Cancer driver" theory considers that tumor initiation can be associated with a number of specific mutations in genes called cancer driver genes. Four omics levels, namely, (1) methylation, (2) microRNA, (3) mutation, and (4) mRNA levels, are utilized to cluster cancer driver genes. In this study, the known dysfunctional genes of these four levels were used to identify novel driver genes of lung adenocarcinoma, a subtype of lung cancer...
December 2, 2017: Biochimica et Biophysica Acta
J Ricardo Arias-Gonzalez
Information is represented by linear strings of symbols with memory that carry errors as a result of their stochastic nature. Proofreading and edition are assumed to improve certainty although such processes may not be effective. Here, we develop a thermodynamic theory for material chains made up of nanoscopic subunits with symbolic meaning in the presence of memory. This framework is based on the characterization of single sequences of symbols constructed under a protocol and is used to derive the behavior of ensembles of sequences similarly constructed...
November 28, 2017: Journal of Chemical Physics
Berit Støre Brinchmann, Cathrine Moe, Mildrid Elisabeth Valvik, Steven Balmbra, Siri Lyngmo, Tove Skarbø
BACKGROUND: Eating disorders are serious conditions which also impact the families of adult patients. There are few qualitative studies of multifamily therapy with adults with severe eating disorders and none concerning the practice of therapists in multifamily therapy. OBJECTIVES: The aim of the study is to explore therapists' practice in multifamily therapy. Research design and participants: A grounded theory approach was chosen. Data were collected through participant observation in two multifamily therapy groups and qualitative interviews with the therapists in those groups...
January 1, 2017: Nursing Ethics
Peng-Wei Zhu, Luguang Chen
In this paper, we investigate the micelle (charge)-constrained collapse of a spherical poly(N-isopropylacrylamide) (PNIPAM) brush. The system is an example of the transition of a short-length neutral polymer from a stretched state to a folded state under the constraint of long-range electrostatic repulsion. The collapsed state is described as an anisotropic globule comprising a cascade of rod-like or hairpin bundles. A critical aggregation number of bound micelles is obtained to distinguish the charge-induced deformation of the globule, which provides a guideline to characterize globule dimensions under different strengths of electrostatic interaction...
November 29, 2017: Physical Chemistry Chemical Physics: PCCP
Antonio Tinti, Alberto Giacomello, Yaroslav Grosu, Carlo Massimo Casciola
Heterogeneous systems composed of hydrophobic nanoporous materials and water are capable, depending on their characteristics, of efficiently dissipating (dampers) or storing ("molecular springs") energy. However, it is difficult to predict their properties based on macroscopic theories-classical capillarity for intrusion and classical nucleation theory (CNT) for extrusion-because of the peculiar behavior of water in extreme confinement. Here we use advanced molecular dynamics techniques to shed light on these nonclassical effects, which are often difficult to investigate directly via experiments, owing to the reduced dimensions of the pores...
November 28, 2017: Proceedings of the National Academy of Sciences of the United States of America
Jiani Chen, Carel Ten Cate
Many animal species can detect dependencies between adjacent visual or auditory items in a string. Compared with adjacent dependencies, detecting nonadjacent dependencies, as present in linguistic constructions, is more challenging as this requires detecting a relation between items irrespective of the number and nature of the intervening items. There is limited evidence that nonhuman animals can detect such dependencies. An animal group in which such abilities might be expected is songbirds, which have learned songs consisting of a series of vocal elements given in specific sequences...
July 2017: Journal of Experimental Psychology. Animal Learning and Cognition
Michael Atiyah, Maciej Dunajski, Lionel J Mason
We review aspects of twistor theory, its aims and achievements spanning the last five decades. In the twistor approach, space-time is secondary with events being derived objects that correspond to compact holomorphic curves in a complex threefold-the twistor space. After giving an elementary construction of this space, we demonstrate how solutions to linear and nonlinear equations of mathematical physics-anti-self-duality equations on Yang-Mills or conformal curvature-can be encoded into twistor cohomology...
October 2017: Proceedings. Mathematical, Physical, and Engineering Sciences
V Swaminathan, Gangothri Rajaram, V Abhishek, Boosi Shashank Reddy, K Kannan
The sequencing by hybridization (SBH) of determining the order in which nucleotides should occur on a DNA string is still under discussion for enhancements on computational intelligence although the next generation of DNA sequencing has come into existence. In the last decade, many works related to graph theory-based DNA sequencing have been carried out in the literature. This paper proposes a method for SBH by integrating hypergraph with genetic algorithm (HGGA) for designing a novel analytic technique to obtain DNA sequence from its spectrum...
November 6, 2017: Interdisciplinary Sciences, Computational Life Sciences
Rivona Harricharan, Oualid Abboussi, William M U Daniels
Over the years, drug addiction has proven to be a perplexing conundrum for scientists. In attempts to decipher the components of the puzzle, multiple theories of addiction have been proposed. While these theories have assisted in providing essential fundamental information, current research recommends that a new theory needs to be presented taking into consideration the results of recent developments in the fields of neuroimmunology, genetics, and neuropsychiatry. After extensively examining the published literature, we propose in this review that neuroinflammation and hypothalamic functioning strongly underpin addictive behavior...
2017: Progress in Brain Research
Ashley A Blackwell, William L Widick, Joseph L Cheatwood, Ian Q Whishaw, Douglas G Wallace
String-pulling by the rat is a bimanual act, in which an upright animal retrieves a piece of food attached to the end of the string by downward hand-over-hand movements. The present study compared the movements of string-pulling, using topographic and kinematic measures of hand movement, in control rats and rats with unilateral sensorimotor motor cortex lesion produced by removal of the pia matter. In the first week following devascularization, the rhythmicity and accuracy of string-pulling movements decomposed; however, thereafter the rhythm of bilateral alternation was restored...
February 15, 2018: Behavioural Brain Research
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