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String theory

S S AbdusSalam
In this article, we show that making global fits of string theory model parameters to data is an interesting mechanism for probing, mapping and forecasting connections of the theory to real world physics. We considered a large volume scenario (LVS) with D3-brane matter fields and supersymmetry breaking. A global fit of the parameters to low-energy data shows that the set of LVS models are associated with light gluinos which are quasi-degenerate with the neutralinos and charginos they can promptly decay into, and thus they are possibly hidden to current LHC gluino search strategies...
2017: European Physical Journal. C, Particles and Fields
Yun Tian, Xiaofei Xu, Jianzhong Wu
We report an efficient computational procedure for rapid and accurate prediction of the self-diffusivity of gas molecules in nanoporous materials by implementing the transitional-state theory for inter-cage hopping at infinite dilution with the string method in conjunction with the excess-entropy scaling for predicting gas diffusion at finite loadings. The theoretical procedure has been calibrated with molecular dynamics simulations for the diffusion coefficients of methane and hydrogen gases in representative nanoporous materials including metal organic frameworks and zeolites...
September 15, 2017: Langmuir: the ACS Journal of Surfaces and Colloids
Jonah Musa, Chad J Achenbach, Linda C O'Dwyer, Charlesnika T Evans, Megan McHugh, Lifang Hou, Melissa A Simon, Robert L Murphy, Neil Jordan
BACKGROUND: Although cervical cancer is largely preventable through screening, detection and treatment of precancerous abnormalities, it remains one of the top causes of cancer-related morbidity and mortality globally. OBJECTIVES: The objective of this systematic review is to understand the evidence of the effect of cervical cancer education compared to control conditions on cervical cancer screening rates in eligible women population at risk of cervical cancer...
2017: PloS One
Xiaoxia He, Yan Shen, Francisco R Hung, Erik E Santiso
Classical molecular dynamics simulations were used to study the nucleation of the crystal phase of the ionic liquid [dmim(+)][Cl(-)] from its supercooled liquid phase, both in the bulk and in contact with a graphitic surface of D = 3 nm. By combining the string method in collective variables [Maragliano et al., J. Chem. Phys. 125, 024106 (2006)], with Markovian milestoning with Voronoi tessellations [Maragliano et al., J. Chem. Theory Comput. 5, 2589-2594 (2009)] and order parameters for molecular crystals [Santiso and Trout, J...
December 7, 2016: Journal of Chemical Physics
Steven M Rosen
This paper carries forward the author's contribution to PBMP's previous special issue on Integral Biomathics (Rosen 2015). In the earlier paper, the crisis in contemporary theoretical physics was described and it was demonstrated that the problem can be addressed effectively only by shifting the foundations of physics from objectivist Cartesian philosophy to phenomenological philosophy. To that end, a phenomenological string theory was proposed based on qualitative topology and hypercomplex numbers. The current presentation takes this further by delving into the ancient Chinese origin of phenomenological string theory...
July 4, 2017: Progress in Biophysics and Molecular Biology
Teresa Schubert, Nicholas Badcock, Saskia Kohnen
Letter recognition and digit recognition are critical skills for literate adults, yet few studies have considered the development of these skills in children. We conducted a nine-alternative forced-choice (9AFC) partial report task with strings of letters and digits, with typographical symbols (e.g., $, @) as a control, to investigate the development of identity and position processing in children. This task allows for the delineation of identity processing (as overall accuracy) and position coding (as the proportion of position errors)...
June 9, 2017: Journal of Experimental Child Psychology
Haipeng Wei, Liyan Zhang, Hoa Phan, Xiaobo Huang, Tun Seng Herng, Jun Zhou, Wangdong Zeng, Jun Ding, Shenglian Luo, Jishan Wu, Zebing Zeng
Organic π-extended radicals display unique electronic structures, and could be used as promising functional materials. However, design and synthesis of stable radicals are challenging for chemists due to their high reactivity. In this work, we synthesized a stable N-annulated perylene-bridged bisphenoxyl diradicaloid, and its complex with Lewis acid boron trifluoride. Their ground-state geometric and electronic structures were systematically studied by various experimental methods, including X-ray crystallographic analysis, variable-temperature NMR spectroscopy, electron-spin resonance spectroscopy (ESR), and superconducting quantum interference device (SQUID) measurements, supported by density functional theory...
May 13, 2017: Chemistry: a European Journal
Tomohiko G Sano, Tetsuo Yamaguchi, Hirofumi Wada
The morphology of an elastic strip subject to vertical compressive stress on a frictional rigid substrate is investigated by a combination of theory and experiment. We find a rich variety of morphologies, which-when the bending elasticity dominates over the effect of gravity-are classified into three distinct types of states: pinned, partially slipped, and completely slipped, depending on the magnitude of the vertical strain and the coefficient of static friction. We develop a theory of elastica under mixed clamped-hinged boundary conditions combined with the Coulomb-Amontons friction law and find excellent quantitative agreement with simulations and controlled physical experiments...
April 28, 2017: Physical Review Letters
Maho Nakata, Tomomi Shimazaki
Large-scale molecular databases play an essential role in the investigation of various subjects such as the development of organic materials, in silico drug design, and data-driven studies with machine learning. We have developed a large-scale quantum chemistry database based on first-principles methods. Our database currently contains the ground-state electronic structures of 3 million molecules based on density functional theory (DFT) at the B3LYP/6-31G* level, and we successively calculated 10 low-lying excited states of over 2 million molecules via time-dependent DFT with the B3LYP functional and the 6-31+G* basis set...
June 26, 2017: Journal of Chemical Information and Modeling
Alex S Arvanitakis, Alec E Barns-Graham, Paul K Townsend
Starting from the classical action for a spin-zero particle in a D-dimensional anti-de Sitter (AdS) spacetime, we recover the Breitenlohner-Freedman bound by quantization. For D=4, 5, 7 and using an Sl(2;K) spinor notation for K=R,C,H, we find a bitwistor form of the action for which the AdS isometry group is linearly realized, although only for zero mass when D=4, 7 in agreement with previous constructions. For zero mass and D=4 the conformal isometry group is linearly realized. We extend these results to the superparticle in the maximally supersymmetric "AdS×S" string or M-theory vacua, showing that quantization yields a 128+128 component supermultiplet...
April 7, 2017: Physical Review Letters
Olaf Hohm
Closed string theory exhibits an O(D,D) duality symmetry on tori, which in double field theory is manifest before compactification. I prove that to first order in α^{'} there is no manifestly background independent and duality invariant formulation of bosonic string theory in terms of a metric, b field, and dilaton. To this end I use O(D,D) invariant second order perturbation theory around flat space to show that the unique background independent candidate expression for the gauge algebra at order α^{'} is inconsistent with the Jacobi identity...
March 31, 2017: Physical Review Letters
Sudip Ghosh, Suvrat Raju
We consider massless string scattering amplitudes in a limit where the number of external particles becomes very large, while the energy of each particle remains small. Using the growth of the volume of the relevant moduli space, and by means of independent numerical evidence, we argue that string perturbation theory breaks down in this limit. We discuss some remarkable implications for the information paradox.
March 31, 2017: Physical Review Letters
Simon Fischer-Baum, Dorothy Bruggemann, Ivan Felipe Gallego, Donald S P Li, Emilio R Tamez
Multiple levels of representation are involved in reading single words: visual representations of letter shape, orthographic representations of letter identity and order, phonological representations of the word's pronunciation, and semantic representations of its meaning. Previous lesion and neuroimaging studies have identified a network of regions recruited during word reading, including ventral occipital-temporal regions and the angular gyrus (AG). However, there is still debate about what information is being represented and processed in these regions...
March 18, 2017: Cortex; a Journal Devoted to the Study of the Nervous System and Behavior
Jonathan Grainger
I will describe how orthographic processing acts as a central interface between visual and linguistic processing during reading, and as such can be considered to be the "mid-level vision" of reading research. In order to make this case, I first summarise the evidence in favour of letter-based word recognition before examining work investigating how orthographic similarities among words influence single word reading. I describe how evidence gradually accumulated against traditional measures of orthographic similarity and the associated theories of orthographic processing, forcing a reconsideration of how letter position information is represented by skilled readers...
April 5, 2017: Quarterly Journal of Experimental Psychology: QJEP
Jonathan Maltz, Leonard Susskind
A quantum mechanical formulation of de Sitter cosmological spacetimes still eludes string theory. In this Letter we conjecture a potentially rigorous framework in which the status of de Sitter space is the same as that of a resonance in a scattering process. We conjecture that transition amplitudes between certain states with asymptotically supersymmetric flat vacua contain resonant pole characteristic metastable intermediate states. A calculation employing constrained instantons illustrates this idea.
March 10, 2017: Physical Review Letters
Eric D'Hoker, Michael Gutperle, Christoph F Uhlemann
We construct global solutions to type IIB supergravity with 16 residual supersymmetries whose space-time is AdS_{6}×S^{2} warped over a Riemann surface. Families of solutions are labeled by an arbitrary number L≥3 of asymptotic regions, in each of which the supergravity fields match those of a (p,q) five-brane, and may therefore be viewed as near-horizon limits of fully localized intersections of five-branes in type IIB string theory. These solutions provide compelling candidates for holographic duals to a large class of five-dimensional superconformal quantum field theories which arise as nontrivial UV fixed points of perturbatively nonrenormalizable Yang-Mills theories, thereby making them more directly accessible to quantitative analysis...
March 10, 2017: Physical Review Letters
Alice Blumenthal-Dramé, Volkmar Glauche, Tobias Bormann, Cornelius Weiller, Mariacristina Musso, Bernd Kortmann
In usage-based linguistic theories, the assumption that high-frequency language strings are mentally represented as unitary chunks has been invoked to account for a wide range of phenomena. However, neurocognitive evidence in support of this assumption is still lacking. In line with Gestalt psychological assumptions, we propose that a language string qualifies as a chunk if the following two conditions are simultaneously satisfied: The perception of the whole string does not involve strong activation of its individual component parts, but the component parts in isolation strongly evoke the whole...
July 2017: Journal of Cognitive Neuroscience
Ignacio Gleria, Esteban Mocskos, Mario Tagliazucchi
A methodology to calculate minimum free-energy paths based on the combination of a molecular theory and the improved string method is introduced and applied to study the self-organization of polymer brushes under poor solvent conditions. Polymer brushes in a poor solvent cannot undergo macroscopic phase separation due to the physical constraint imposed by the grafting points; therefore, they microphase separate forming aggregates. Under some conditions, the theory predicts that the homogeneous brush and the aggregates can exist as two different minima of the free energy...
March 9, 2017: Soft Matter
Andrew Currin, Konstantin Korovin, Maria Ababi, Katherine Roper, Douglas B Kell, Philip J Day, Ross D King
The theory of computer science is based around universal Turing machines (UTMs): abstract machines able to execute all possible algorithms. Modern digital computers are physical embodiments of classical UTMs. For the most important class of problem in computer science, non-deterministic polynomial complete problems, non-deterministic UTMs (NUTMs) are theoretically exponentially faster than both classical UTMs and quantum mechanical UTMs (QUTMs). However, no attempt has previously been made to build an NUTM, and their construction has been regarded as impossible...
March 2017: Journal of the Royal Society, Interface
Andrew J Milat, Ben Li
BACKGROUND: A significant challenge in research translation is that interested parties interpret and apply the associated terms and conceptual frameworks in different ways. The purpose of this review was to: a) examine different research translation frameworks; b) examine the similarities and differences between the frameworks; and c) identify key strengths and weaknesses of the models when they are applied in practice. METHODS: The review involved a keyword search of PubMed...
February 15, 2017: Public Health Research & Practice
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