Massachusetts Institute of Technology. Dept. of Physics. Thesis. 1972. Ph.D. / MICROFICHE COPY ALSO AVAILABLE IN SCIENCE LIBRARY. / Vita. / Includes bibliographical references. / Ph.D.

Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Physics, 2008. / Includes bibliographical references (p. 179-194). / At present, there are no non-perturbative analytic methods available for investigating gauge theories at large couplings. Consequently, it is desirable to explore more avenues to gain qualitative and quantitative insights. The gauge/gravity (AdS/CFT) correspondences provides a unique opportunity to study gauge theories both at finite and zero temperatures in the strong coupling regime, potentially leading to insights into QCD. In this regime, where both the 't Hooft coupling and the number of colors is large, the dynamics of the gauge theory is described by super gravity solutions, which describe the low-energy limit of systems of D-branes. In this dissertation, I use the AdS/CFT correspondence to study the dispersion relations of mesons in a particular hot, strongly coupled, supersymmetric gauge theory plasma. This plasma arises by placing a probe D7-brane in the near-horizon geometry of non-extremal D3-branes. I find the large momentum dispersion relations of scalar mesons and extract from them their limiting velocity vo, which depends only on the ratio of the temperature to the quark mass. I use vo to find that the temperature above which no meson bound states with velocity v exist is Tdiss(V) - (1 - v2)1/4Tdiss(v = 0). This agrees with results inferred indirectly via analysis of the screening length between a static quark and anti quark in a moving plasma. Although these calculations are not done in QCD, I argue that the qualitative features of my results may apply to bottomonium and charmonium mesons propagating in the strongly coupled QCD plasma. To aid further investigations of the effect of fundamental matter on hot gauge theory plasmas I find the non-extremal, localized D2/D6-brane solution in its linear limit. Pursuing a different direction, I consider a stack of N D3-branes and M D5-branes wrapped at the apex of a cone over Sasaki- Einstein spaces yp,q. Replacing the D-branes by their fluxes, I construct asymptotic solutions for all p and q in the form of warped products of the cone and R" 3. These theories are not conformal, and the solutions describe cascading renormalization group flows. / by Qudsia Jabeen Ejaz. / Ph.D.

Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Physics, 1998. / Includes bibliographical references (p. 191-199). / by Neal W. Spellmeyer. / Ph.D.

Thesis: Ph. D., Massachusetts Institute of Technology, Department of Physics, 2016. / Cataloged from PDF version of thesis. / Includes bibliographical references (pages 217-232). / Two dijet measurements, one using 35 pb-¹ pPb data at [square root]sNN- 5.02 TeV, and another with 166 [mu]b-¹ PbPb and 5.3 pb-¹ pp data at [square root]sNN = 2.76 TeV collected with CMS detector at the LHC, are presented. In pPb collisions, the dijet PT ratios, azimuthal angle differences and pseudorapidity distributions are measured and compared to PYTHIA and PYTHIA+HIJING simulations as well as NLO QCD predictions for the latter observable. No significant signs of final state interactions, such as a decrease in the mean dijet PT ratios or a broadening in the correlation of the dijets in azimuthal angle, with increasing forward activity, are observed. The dijet pseudorapidity distributions are also measured, and are sensitive to nuclear PDFs for x values of 0.001 - 0.5. Selections on event activity are found to yield unexpected centrality biases on dijet pseudorapidity distributions, which aided the interpretation of similar biases seen in inclusive jet measurements by ATLAS. In PbPb collisions, a detailed scan of charged particle distributions in correlation with the dijet system is carried out. The PT projection of charged particles on the dijet axis is measured at different distances of [delta] = [mathematical formula ...] 2 with respect to the leading and subleading jet axes. In this way, the spectra and angular distribution of the additional particles, which recover the overall event balance in dijet events with enhanced PT asymmetry in PbPb compared to pp collisions, are obtained up to [delta] = 1.8 in steps of 0.2. A significant excess of low PT particles associated with a subleading jet at large [delta] values is observed, and this excess is shown to get larger for dijet events with PT asymmetry. The scan is carried out for variety of anti-kT R parameters, which provides a way of varying jet width and fragmentation. Medium response to jet quenching at wide angles for jets with different fragmentation is studied. Only an insignificant increase of the magnitude of low PT particle excess at large angles, but a significant increase in the modification of the balance distribution close to the jet axes is observed by increasing R. / by Doga C. Gulhan. / Ph. D.

Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Physics, 2003. / Includes bibliographical references (p. 177-182). / This electronic version was submitted by the student author. The certified thesis is available in the Institute Archives and Special Collections. / We investigate color superconducting phases of cold quark matter at densities relevant for the interiors of compact stars. At these densities, electrically neutral and weak-equilibrated quark matter can have unequal numbers of up, down, and strange quarks. The QCD interaction favors Cooper pairs that are antisymmetric in color and in flavor, and a crystalline color superconducting phase can occur which accommodates pairing between flavors with unequal number densities. In the crystalline color superconductor, quarks of different flavor form Cooper pairs with nonzero total momentum, yielding a condensate that varies in space like a sum of plane waves. Rotational and translational symmetry are spontaneously broken. We use a Ginzburg-Landau method to evaluate candidate crystal structures and predict that the favored structure is face-centered-cubic. We predict a robust crystalline phase with gaps comparable in magnitude to those of the color-flavor-locked phase that occurs when the flavor number densities are equal. Crystalline color superconductivity will be a generic feature of the QCD phase diagram, occurring wherever quark matter that is not color-flavor locked is to be found. If a very large flavor asymmetry forbids even the crystalline state, single-flavor pairing will occur; we investigate this and other spin-one color superconductors in a survey of generic color, flavor, and spin pairing channels. Our predictions for the crystalline phase may be tested in an ultracold gas of fermionic atoms, where a similar crystalline superfluid state can occur. If a layer of crystalline quark matter occurs inside of a compact star, it could pin rotational vortices, leading to observable pulsar glitches. / by Jeffrey Allan Bowers / Ph.D.

Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Physics, 1997. / Includes bibliographical references (p. 107-109). / by Changnan Wang. / Ph.D.

Thesis: S.B., Massachusetts Institute of Technology, Department of Physics, 2014. / Cataloged from PDF version of thesis. / Includes bibliographical references (pages 69-73). / This thesis analyzes HD 82074, a solar-mass and low-metallicity subgiant star, using ground-based asteroseismology with the CHIRON spectrometer at the Cerro Tololo Inter-American Observatory (CTIO) and interferometry with the CHARA array on Mt. Wilson. The physical parameters of subgiant stars are of particular interest in the exoplanetary field due to their importance in understanding the relationships between planet occurrence rate and stellar properties such as age, metallicity and mass. Potential systematic uncertainties in the canonical stellar models make it especially important to independently determine the masses and radii of these stars. We determine HD 82074's radius using interferometry from CHARA, and we combine this result with measurements of the spacing and frequencies of the asteroseismic oscillations of HD 82074 to determine a stellar mass. We find that the star has a radius of 3.96 0.12 solar radii and a mass of 1.20 0.11 solar masses. While the radius is in excellent agreement with predictions from spectral analysis, the mass is 2.9-o- greater than the predicted mass. This suggests that errors of stellar models may be underestimated for low-metollicity or evolved stars. This study makes HD 82074 the third subgiant for which a physical radius is confirmed interferometrically and one of ten asteroseismically studied subgiants. / by Victoria Ashley Villar. / S.B.

Thesis (B.S.)--Massachusetts Institute of Technology, Dept. of Physics, 1959. / MIT copy bound with: Ground state reaction energy determination for K⁴¹(p,α)A³⁸ / Robert William Bird and Theodore Neil Divine. 1959. / Includes bibliographical references (leaves 16-18). / by Robert Peel Futrelle. / B.S.

Thesis (S.B.)--Massachusetts Institute of Technology, Dept. of Physics, 2008. / Includes bibliographical references (p. 51). / The purpose of this thesis is to investigate both the qualitative and quantitative effects of including higher order amplitude terms in the post-Newtonian expansion for gravitational waves on parameter estimation of inspiraling binary systems. First, we review the mechanism behind gravitational wave production and the formalism behind our estimation of parameters given a specific waveform. Then, we use a Monte Carlo simulation of 1000 separate binary systems with random position, and orientation parameters and fixed mass ratios between binary objects to generate gravitational waveforms measurements from a detector model which mimics data received from the proposed LISA mission. After that we numerically estimate how well those parameters are determined. The data presented compares median values of accuracy defined as Aý/ý for parameters ( of luminosity distance, chirp mass, and reduced mass, as well as the major and minor axes of a localization ellipse between waveform models which include only the leading quadrupole harmonic amplitude contribution, and the .5PN amplitude harmonic correction to the quadrupole. Our results show that, for all the Monte Carlo simulations run, there is a substantial global improvement in accuracy of the estimated parameters when higher order .5PN amplitude terms are included in the waveform model. The largest improvement shown comes from the range of masses between 105 and 106 solar masses, which is the ideal reception band for the LISA detector array. This improvement can eventually be applicable to aid in the location of binary sources for confirmation of direct gravitational wave observation. We conclude from these results that it is indeed advantageous to include higher order terms in the post-Newtonian expansion for gravitational wave models in order to obtain more accurate parameter estimates. / by Terrence J. Torres. / S.B.

Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Physics, 2008. / Includes bibliographical references (p. 167-180). / Graphene, a one-atom-thick form of carbon, has emerged in the last few years as a fertile electron system, highly promising for both fundamental research and applications. In this thesis we consider several topics in electronic and spin properties of graphene, with a particular emphasis on the quantum Hall effect (QHE) regime, where this material exhibits most interesting behavior. We shall start with analyzing general properties of the two-terminal conductance for graphene mono- and bilayer samples. Using conformal invariance and the theory of conformal mappings, we characterize the dependence of conductance on the sample shape. We identify the features which distinguish monolayers and bilayers and illustrate the use of the two-terminal conductance as a tool for sample diagnostic. Next, we present a microscopic study of the edge states in the QHE regime. This analysis provides a simple and general explanation of the half-integer Hall quantization in graphene. We discuss the edge states dispersion for different orientations of the boundary, and propose a way to image the edge states using STM spectroscopy. Then, we extend the picture of edge states to describe QHE in spatially nonuniform systems, recently demonstrated p-n and p-n-p devices. We show that the bipolar p-n and p-n-p junctions can host counter-circulating QHE edge states, which mix at the p-n interfaces, giving rise to fractional and integer quantization of the two-terminal conductance, observed in this structures. Graphene exhibits interesting spin- and valley-polarized QH ferromagnetic (FM) states. We show that spin-polarized QH state at zero doping hosts counter-circulating edge states carrying opposite spins, and propose to use this regime as a vehicle to study spin transport. We study ordering in the valley-polarized QH state. / (cont.) Coupling of valley QHFM order parameter to random strain-induced vector potential yields an easy-plane-type ordering of the valley QHFM, giving rise to Berezinskii-Kosterlitz-Thouless transition, with fractionally charged vortices (merons) in the ordered state. / by Dmitry A. Abanin. / Ph.D.