Página 1 dos resultados de 481279 itens digitais encontrados em 0.115 segundos

Physics and computation

Margolus, Norman
Fonte: Massachusetts Institute of Technology Publicador: Massachusetts Institute of Technology
Tipo: Tese de Doutorado Formato: 243 p.; 12520193 bytes; 12519951 bytes; application/pdf; application/pdf
ENG
Relevância na Pesquisa
45.32%
by Norman H. Margolus.; Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Physics, 1987.; Bibliography: leaves 235-243.

The eikonal expansion in electromagnetic nuclear physics

Kronenberg, Eric Leslie
Fonte: Massachusetts Institute of Technology Publicador: Massachusetts Institute of Technology
Tipo: Tese de Doutorado Formato: 216 p.; 16999693 bytes; 16999449 bytes; application/pdf; application/pdf
ENG
Relevância na Pesquisa
45.32%
by Eric Leslie Kronenberg.; Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Physics, 1989.; GRSN 406579; Includes bibliographical references (p. 209-213).

Physics of liquid crystals embedded in silica gels

Park, Sungil, 1967-
Fonte: Massachusetts Institute of Technology Publicador: Massachusetts Institute of Technology
Tipo: Tese de Doutorado Formato: 130 p.; 7871755 bytes; 7871513 bytes; application/pdf; application/pdf
ENG
Relevância na Pesquisa
45.32%
Octylcyanobiphenyl (8CB) embedded in silica aerosil gels have been studied by means of high resolution X-ray scattering experiments. The silica particles form a hydrogen-bonded fractal gel network that introduces quenched disorder. As a result, the nematic to smectic-A transition is replaced by the growth of static short range smectic correlations. The X-ray scattering profile has two contributions: a thermal fluctuation term which resembles that of the pure liquid crystal and a static fluctuation term due to the random field that becomes important at low temperatures. The decrease of the smectic correlations with increasing silica density is consistent with theory and other experiments.; by Sungil Park.; Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Physics, 2001.; Includes bibliographical references (p. 127-130).

Multiscale ab initio approaches to materials physics

Engeness, Torkel Dyrbaek, 1972-
Fonte: Massachusetts Institute of Technology Publicador: Massachusetts Institute of Technology
Tipo: Tese de Doutorado Formato: 162 leaves; 10186394 bytes; 10186152 bytes; application/pdf; application/pdf
ENG
Relevância na Pesquisa
45.34%
This work presents new ab initio approaches to materials physics. We first introduce the multiscale approach to determination of thermal properties and changes in free energy. With this approach one can perform thermal averaging of ensembles of states with ab initio methods, thus enabling ab initio calculations of free energy changes. We use this method to perform an ab initio calculation of the free energy of reconstruction in the 300 reconstruction of silicon. In the next chapters we introduce a completely new approach to electronic structure calculations, using a new, real-space bais set (wavelets) which enables all-electron calculations of complex systems. By eliminating the need for pseudopotentials for decsribing the core, one can for the first time access the true density functional energy of a system through systematic convergence. In the final chapter we combine this method with the generalized gradient approximation to perform calculations on high-pressure phases of boron.; by Torkel D. Engeness.; Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Physics, 2003.; Includes bibliographical references (leaves 157-162).

Statistical physics and biological information : hydrophobicity patterns in protein design and differential motif finding in DNA; Hydrophobicity patterns in protein design and differential motif finding in DNA

Yahyanejad, Mehdi, 1975-
Fonte: Massachusetts Institute of Technology Publicador: Massachusetts Institute of Technology
Tipo: Tese de Doutorado Formato: 124 p.; 4734447 bytes; 4750021 bytes; application/pdf; application/pdf
EN_US
Relevância na Pesquisa
45.34%
(cont.) is dictated by the solvent accessibility of structures. The distinct intrinsic tendencies of sequence and structure profiles are most pronounced at long periods, where sequence hydrophobicity fluctuates less, while solvent accessibility fluctuates more than average. Correlations between the two profiles can be interpreted as the Boltzmann weight of the solvation energy at room temperature. Chapter 4 shows that correlations in solvent accessibility along protein structures play a key role in the designability phenomenon, for both lattice and natural proteins. Without such correlations, as predicted by the Random Energy Model (REM), all structures will have almost equal values of designability. By using a toy, Ising-based model, we show that changing the correlations moves between a regime with no designability and a regime exhibiting the designability phenomenon, where a few highly designable structures emerge. Understanding how gene expression is regulated is one of the main goals of molecular cell biology. To reach this goal, the recognition and identification of DNA motifs--short patterns in biological sequences--is essential. Common examples of motifs include transcription factor binding sites in promoter regions of co-regulated genes and exonic and intronic splicing enhancers ...; In the past decade...

Statistical physics of dislocation nucleation by nanoindentation

Mason, Jeremy K. (Jeremy Kyle)
Fonte: Massachusetts Institute of Technology Publicador: Massachusetts Institute of Technology
Tipo: Tese de Doutorado Formato: 82 p.; 4154940 bytes; 4158610 bytes; application/pdf; application/pdf
ENG
Relevância na Pesquisa
45.32%
Current understanding of the onset of plasticity during nanoindentation of crystalline materials involves homogenous dislocation nucleation in the crystal underneath the indenter. Through the use of cutting-edge nanoindentation techniques, this study examines the initiation of plastic deformation in single crystal oriented platinum samples. Variations in the temperature and loading rate during indentation reveal temporal and thermal dependencies, and support the stochastic and thermally-activated nature of the initial plastic event. These dependencies of dislocation nucleation are precisely quantified by developing analysis methods based on statistical thermodynamics, and are used to evaluate the probability of various atomistic mechanisms. The results of this procedure implicate a critical activation event occurring in a single atomic volume, with an activation enthalpy of a fraction of an electron volt. These findings strongly indicate that the initiation of plasticity begins with a heterogeneous dislocation nucleation event, in conflict with the current belief, and significantly advance understanding of the onset of plastic deformation during nanoindentation.; by Jeremy K. Mason.; Thesis (S.B.)--Massachusetts Institute of Technology...

Applications of particle physics to the early universe

Senatore, Leonardo
Fonte: Massachusetts Institute of Technology Publicador: Massachusetts Institute of Technology
Tipo: Tese de Doutorado Formato: 190 p.
ENG
Relevância na Pesquisa
45.35%
In this thesis, I show some of the results of my research work in the field at the crossing between Cosmology and Particle Physics. The Cosmology of several models of the Physics Beyond the Standard Model is studied. These range from an inflationary model based on the condensation of a ghost-like scalar field, to several models motivated by the possibility that our theory is described by a landscape of vacua, as probably implied by String Theory, which have influence on the theory of Baryogenesis, of Dark Matter, and of Big Bang Nucleosynthesis. The analysis of the data of the experiment WMAP on the CMB for the search of a non-Gaussian signal is also presented and it results in an upper limit on the amount on non-Gaussianities which is at present the most precise and extended available.; by Leonardo Senatore.; Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Physics, 2006.; Includes bibliographical references (p. 182-186).

Robustness and infrared sensitivity of various observables in the application of AdS/CFT to heavy ion physics

Shi, Yeming
Fonte: Massachusetts Institute of Technology Publicador: Massachusetts Institute of Technology
Tipo: Tese de Doutorado Formato: 73 p.
ENG
Relevância na Pesquisa
45.32%
We investigate the robustness with respect to the introduction of nonconformality of five properties of strongly coupled plasmas that have been calculated in K = 4 supersymmetric Yang-Mills (SYM) theory at nonzero temperature, motivated by the goal of understanding phenomena in relativistic heavy ion collisions. (The five properties are the jet quenching parameter, the velocity dependence of screening, and the drag and transverse and longitudinal momentum diffusion coefficients for a heavy quark pulled through the plasma.) We do so using a toy model in which nonconformality is introduced via a one-parameter deformation of the AdS black hole dual to the hot KN = 4 SYM plasma. For values of this parameter which correspond to a degree of nonconformality comparable to that seen in lattice calculations of QCD thermodynamics at temperatures a few times that of the crossover to quark-gluon plasma, we find that the jet quenching parameter is affected by the nonconformality at the 30% level or less, the screening length is affected at the 20% level or less, but the drag and diffusion coefficients for a slowly moving heavy quark can be modified by as much as 80%. However, we show that all but one of the five properties that we investigate become completely insensitive to the nonconformality in the high velocity limit v --...

Model independent search for new physics at the Tevatron

Choudalakis, Georgios
Fonte: Massachusetts Institute of Technology Publicador: Massachusetts Institute of Technology
Tipo: Tese de Doutorado Formato: 242 p.
ENG
Relevância na Pesquisa
45.37%
The Standard Model of elementary particles can not be the final theory. There are theoretical reasons to expect the appearance of new physics, possibly at the energy scale of few TeV. Several possible theories of new physics have been proposed, each with unknown probability to be confirmed. Instead of arbitrarily choosing to examine one of those theories, this thesis is about searching for any sign of new physics in a model-independent way. This search is performed at the Collider Detector at Fermilab (CDF). The Standard Model prediction is implemented in all final states simultaneously, and an array of statistical probes is employed to search for significant discrepancies between data and prediction. The probes are sensitive to overall population discrepancies, shape disagreements in distributions of kinematic quantities of final particles, excesses of events of large total transverse momentum, and local excesses of data expected from resonances due to new massive particles. The result of this search, first in 1 fb-1 and then in 2 fb-1, is null, namely no considerable evidence of new physics was found.; by Georgios Choudalakis.; Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Physics, 2008.; Includes bibliographical references (p. 235-242).

The design and implementation of a peer learning programme in physics utilising undergraduate peer leaders: an in-depth investigation into the effect of participation and the experience of the peer leaders

Fonte: University of Limerick, Department of Physics Publicador: University of Limerick, Department of Physics
Tipo: Doctoral thesis; all_ul_research; ul_theses_dissertations; none
ENG
Relevância na Pesquisa
45.39%
peer-reviewed; Physics Education Research (PER) has shown that students leave the physics classroom holding the same misconceptions about physics they had when they entered. PER has demonstrated that these misconceptions are often deeply held and are difficult to change. The literature indicates that Peer Learning has advantages compared with traditional methods in producing conceptual change and that there are a number of potential benefits for utilising undergraduates as Peer Leaders in Peer Learning programmes. Gartner, Kohler, and Riessman (1971) summarised a number of beneficial cognitive processes that occur when Peer Leaders prepare for Peer Learning sessions. It is believed that in reviewing, organising and teaching the material, they may gain a better understanding of the subject. However, little or no literature exists on the effect participation has on Peer Leaders or their experience of a Peer Learning programme. In particular, few studies determining the effect of participation on the Peer Leaders in physics at third level exist. The purpose of this study is to explore the effect of becoming a Peer Leader, to investigate the experience of becoming a Peer Leader, and to illuminate the implications of using undergraduate Peer Leaders in physics tutorials at third level. A model of Peer Learning was designed and implemented in physics tutorials at the University of Limerick and the Peer Leaders selected for this study had direct experience of undergraduate introductory physics courses. This Peer Learning model involved students working in cooperative groups with an undergraduate Peer Leader as a facilitator of their learning. Training was provided to the Peer Leaders to ensure that they created an environment where the students were actively and productively engaged with the material and with each other. Action research was chosen as the central methodology of this thesis...

The rise and fall of structure in physics : polaritonic photonic crystals, melting, and min-protein oscillations

Huang, Kerwyn Casey, 1979-
Fonte: Massachusetts Institute of Technology Publicador: Massachusetts Institute of Technology
Tipo: Tese de Doutorado Formato: 197 p.; 10306933 bytes; 10332161 bytes; application/pdf; application/pdf
EN_US
Relevância na Pesquisa
45.34%
This thesis is a compilation of theoretical and computational work in condensed matter physics related to three topics in structure development. First, I study photonic crystals composed of polaritonic media, focusing on the unique features of the band structures and Bloch states in dispersive media with and without losses. I discuss three novel localization phenomena in these structures: node switching, flux expulsion, and negative effective permeability. Second, I examine the importance of surface interfaces to melting using density functional theory. I demonstrate that single-layer coatings of Gallium Arsenide on Germanium and vice versa have a huge impact on the substrate melting temperature, causing superheating and induced melting, respectively. Finally, I develop reaction-diffusion and stochastic models of the Min-protein oscillations in bacteria that reproduce all main experimental observations. These models explain the origin of instability that ultimately causes dynamic pattern formation and have successfully been used to predict nucleotide binding rates in E. coli. In round cells, I provide evidence that oscillations can be used as a general mechanism for protein targeting and detecting the cell's geometry.; by Kerwyn Casey Huang.; Thesis (Ph. D.)--Massachusetts Institute of Technology...

A quasi-model-independent search strategy for new high-pT physics at Tevatron Run II

Lee, Jang Woo, 1973-
Fonte: Massachusetts Institute of Technology Publicador: Massachusetts Institute of Technology
Tipo: Tese de Doutorado Formato: 105 p.; 4763518 bytes; 4775937 bytes; application/pdf; application/pdf
EN_US
Relevância na Pesquisa
45.37%
Compelling arguments suggest the presence of new physics at the electroweak scale, an energy regime accessible to the Fermilab Tevatron. Unfortunately, predictions for the form that new physics will take are all over the map. A quasi-model-independent search strategy for new physics (SLEUTH) was introduced in Tevatron Run I to allow a probe of high-pT hadron collider data. This dissertation prescribes the SLEUTH algorithm that will be used in Tevatron Run II. Improvements over the Run I algorithm are discussed, and an intuition is developed for SLEUTH'S performance by considering a number of beyond-the-standard-model examples. This dissertation defines a priori the SLEUTH algorithm, before its application to Tevatron Run II data, allowing an unbiased and rigorous a posteriori measure of the "interestingness" of any observed signal. This algorithm will also be used with small modifications at the Large Hadron Collider at CERN. In addition, a new detector simulation, TurboSim, was tested for physics analysis use for the first time.; by Jang Woo Lee.; Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Physics, 2004.; Includes bibliographical references (p. 103-105).

Analysis and Projections of Physics in Chile

Lund, Fernando; Molina Gálvez, Mario Ignacio; Gutiérrez, Gonzalo; Zambra, Marcelo; Haberle, Patricio; Barra de la Guarda, Felipe Javier; Loewe, Marcelo; Saavedra, Carlos; Soto, Leopoldo
Fonte: Institute of Physics (IoP) Publicador: Institute of Physics (IoP)
Tipo: Artículo de revista
EN
Relevância na Pesquisa
45.39%
In the present work, an assessment of the Physics research capacity in Chile is presented. For this, the period between 2000 and June 2005 has been studied. In this period almost 200 physicists have contributed to scientific production in terms of ISI publications. Amongst these 200, ~160 correspond to theoretical physicists and only ~40 to experimental physicists; ~178 are men and only ~22 are women. A more detailed analysis shows that ~160 physicists have at least one appearance in ISI publications per year considering the last 3 years. Ten years ago, a similar criteria (at least one appearance per year in ISI articles, considering mobile three-year periods), the number of active physicists in the Chilean community was estimated at 70. Therefore, the Chilean active physicists’ community has doubled in 10 years. There exist 20 centres in which scientific research is developed: 18 university centres, a government institute and a private institute. As regards scientific productivity, both as related to disciplines or research areas, and well as in relation to research centres, it is found that, generally, scientific production, in a particular area in Physics or in a research centre, is directly related to the number of corresponding researchers; that is to say...

Physics at the CLIC Multi-TeV Linear Collider

CLIC Physics Working Group; Accomando, E.; Aranda, A.; Ateser, E.; Balazs, C.; Bardin, D.; Barklow, T.; Battaglia, M.; Beenakker, W.; Berge, S.; Blair, G.; Boos, E.; Boudjema, F.; Braun, H.; Burikham, P.; Burkhardt, H.; Cacciari, M.; Cakir, O.; Ciftci, A.
Fonte: Universidade Cornell Publicador: Universidade Cornell
Tipo: Artigo de Revista Científica
Publicado em 17/12/2004
Relevância na Pesquisa
45.37%
This report summarizes a study of the physics potential of the CLIC e+e- linear collider operating at centre-of-mass energies from 1 TeV to 5 TeV with luminosity of the order of 10^35 cm^-2 s^-1. First, the CLIC collider complex is surveyed, with emphasis on aspects related to its physics capabilities, particularly the luminosity and energy, and also possible polarization, \gamma\gamma and e-e- collisions. The next CLIC Test facility, CTF3, and its R&D programme are also reviewed. We then discuss aspects of experimentation at CLIC, including backgrounds and experimental conditions, and present a conceptual detector design used in the physics analyses, most of which use the nominal CLIC centre-of-mass energy of 3 TeV. CLIC contributions to Higgs physics could include completing the profile of a light Higgs boson by measuring rare decays and reconstructing the Higgs potential, or discovering one or more heavy Higgs bosons, or probing CP violation in the Higgs sector. Turning to physics beyond the Standard Model, CLIC might be able to complete the supersymmetric spectrum and make more precise measurements of sparticles detected previously at the LHC or a lower-energy linear e+e- collider: \gamma\gamma collisions and polarization would be particularly useful for these tasks. CLIC would also have unique capabilities for probing other possible extensions of the Standard Model...

Physics and Technology of the Next Linear Collider: A Report Submitted to Snowmass '96

NLC ZDR Design Group; NLC Physics Working Group; Kuhlman, S.
Fonte: Universidade Cornell Publicador: Universidade Cornell
Tipo: Artigo de Revista Científica
Publicado em 30/05/1996
Relevância na Pesquisa
45.36%
We present the current expectations for the design and physics program of an e+e- linear collider of center of mass energy 500 GeV -- 1 TeV. We review the experiments that would be carried out at this facility and demonstrate its key role in exploring physics beyond the Standard Model over the full range of theoretical possibilities. We then show the feasibility of constructing this machine, by reviewing the current status of linear collider technology and by presenting a precis of our `zeroth-order' design.; Comment: 207 pages, 98 figures; tar'ed and gzip'ed source is 1.5MB, PS file is 11MB, 1.8 MB gzip'ed. 8 figures bitmapped at 100dpi. Full PS file with higher resolution figures available at http://www.slac.stanford.edu/accel/nlc/physics-review/

Physics at a future Neutrino Factory and super-beam facility

The ISS Physics Working Group
Fonte: Universidade Cornell Publicador: Universidade Cornell
Tipo: Artigo de Revista Científica
Relevância na Pesquisa
45.35%
The conclusions of the Physics Working Group of the international scoping study of a future Neutrino Factory and super-beam facility (the ISS) are presented. The ISS was carried by the international community between NuFact05, (the 7th International Workshop on Neutrino Factories and Superbeams, Laboratori Nazionali di Frascati, Rome, June 21-26, 2005) and NuFact06 (Ivine, California, 24{30 August 2006). The physics case for an extensive experimental programme to understand the properties of the neutrino is presented and the role of high-precision measurements of neutrino oscillations within this programme is discussed in detail. The performance of second generation super-beam experiments, beta-beam facilities, and the Neutrino Factory are evaluated and a quantitative comparison of the discovery potential of the three classes of facility is presented. High-precision studies of the properties of the muon are complementary to the study of neutrino oscillations. The Neutrino Factory has the potential to provide extremely intense muon beams and the physics potential of such beams is discussed in the final section of the report.; Comment: 370 pages, 121 postscript figures

Physics highlights at ILC and CLIC

Lukić, Strahinja; Collaboration, on behalf of the FCAL; Detector, the CLIC; Study, Physics
Fonte: Universidade Cornell Publicador: Universidade Cornell
Tipo: Artigo de Revista Científica
Publicado em 17/06/2014
Relevância na Pesquisa
45.38%
In this lecture, the physics potential for the e+e- linear collider experiments ILC and CLIC is reviewed. The experimental conditions are compared to those at hadron colliders and their intrinsic value for precision experiments, complementary to the hadron colliders, is discussed. The detector concepts for ILC and CLIC are outlined in their most important aspects related to the precision physics. Highlights from the physics program and from the benchmark studies are given. It is shown that linear colliders are a promising tool, complementing the LHC in essential ways to test the Standard Model and to search for new physics.; Comment: 15 pages, 9 figures, presented at the 12th International School-Seminar "The Actual Problems of Microworld Physics" in Gomel, Belarus, July 22 - August 2, 2013

Heavy quark physics on the lattice with improved nonrelativistic actions

Meinel, Stefan
Fonte: University of Cambridge; Department of Applied Mathematics and Theoretical Physics; St John's College Publicador: University of Cambridge; Department of Applied Mathematics and Theoretical Physics; St John's College
Tipo: Thesis; doctoral; PhD
EN
Relevância na Pesquisa
45.34%
Hadrons containing heavy quarks, in particular b quarks, play an important role in high energy physics. Measurements of their electroweak interactions are used to test the Standard Model and search for new physics. For the comparison of experimental results with theoretical predictions, nonperturbative calculations of hadronic matrix elements within the theory of quantum chromodymanics are required. Such calculations can be performed from first principles by formulating QCD on a Euclidean spacetime grid and computing the path integral numerically. Including b quarks in lattice QCD calculations requires special techniques as the lattice spacing in present computations usually can not be chosen fine enough to resolve their Compton wavelength. In this work, improved nonrelativistic lattice actions for heavy quarks are used to perform calculations of the bottom hadron mass spectrum and of form factors for heavy-to-light decays. In heavy-to-light decays, additional complications arise at high recoil, when the momentum of the light meson reaches a magnitude comparable to the cutoff imposed by the lattice. Discretisation errors at high recoil can be reduced by working in a frame of reference where the heavy and light mesons move in opposite directions. Using a formalism referred to as moving nonrelativistic QCD (mNRQCD)...

Estimation of the Z->vv background to New Physics searches in ATLAS

Sandoval, Tanya
Fonte: University of Cambridge; Department of Physics; Wolfson College; CERN; Cavendish Laboratory Publicador: University of Cambridge; Department of Physics; Wolfson College; CERN; Cavendish Laboratory
Tipo: Thesis; doctoral; PhD
EN
Relevância na Pesquisa
45.34%
This thesis describes a series of studies related to searches for new phenomena, beyond the Standard Model of particle physics, in high energy hadron collisions. In such searches, it becomes crucial to identify the Standard Model backgrounds in order to resolve a potential new signal. The thesis presents a method that uses photon events to determine one of such backgrounds, caused by the production of Z boson events. The studies performed to validate the method, both theoretically and experimentally, are presented and the method was shown to be successful as well as to provide reliable results. Theoretically, the method is found to be robust up to a ~10% uncertainty. Experimentally, the method is implemented to estimate the Z(vv) + jets background for the SUSY 0l + E_T^miss + jets search in the ATLAS experiment at the Large Hadron Collider, where this background is one of the most important components for the final sensitivity and is impossible to measure directly. The main experimental results presented are the latest from ATLAS at the time of writing, corresponding to the full dataset of proton-proton collisions delivered by the LHC in 2011 (4.7 fb^-1) at a centre of mass energy of 7 TeV. Given that this method has been mainstream since 2010...

Phenomenological aspects of new physics at high energy hadron colliders

Papaefstathiou, Andreas
Fonte: University of Cambridge; Department of Physics Publicador: University of Cambridge; Department of Physics
Tipo: Thesis; doctoral; PhD
EN
Relevância na Pesquisa
45.36%
This thesis contains studies of phenomenological aspects of new physics at hadron colliders, such as the Large Hadron Collider (LHC). After a general introduction in chap- ter 1, in chapter 2 we outline the main features of the Standard Model (SM) of particle physics and the theoretical motivations for going beyond it. We subsequently provide brief descriptions of a few popular models that aim to solve the issues that arise within the SM. In chapter 3 we describe the general Monte Carlo method for evaluating multidimen- sional integrals and show how it can be used to construct a class of computational tools called Monte Carlo event generators. We describe the main generic features of event generators and how these are implemented in the HERWIG++ event generator. By applying resummation techniques, we provide, in chapter 4, analytical calcula- tions of two types of hadron collider observables. The first, global inclusive variables, are observables that make use of all measured particle momenta and can provide useful information on the scale of new physics. The second observable is the transverse energy of the QCD initial state radiation (ET ), associated with the either Drell-Yan gauge boson production or Higgs boson production. In both cases we provide comparisons to results obtained from Monte Carlo event generators. In chapter 5 we examine two well-motivated models for new physics: one of new heavy charged vector bosons (W prime)...