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Item 125 gev higgs boson mass from 5d gauge-higgs unification(University of Alabama Libraries, 2015) Carson, Jason Carl; Okada, Nobuchika; University of Alabama TuscaloosaShow more In the context of a simple gauge-Higgs unification (GHU) scenario based on the gauge group SU(3)×U(1)′ in a 5-dimensional flat space-time, we investigate a possibility to reproduce the observed Higgs boson mass of around 125 GeV. We introduce bulk fermion multiplets with a bulk mass and a (half) periodic boundary condition. In our analysis, we adopt a low energy effective theoretical approach of the GHU scenario, where the running Higgs quartic coupling is required to vanish at the compactification scale. Under this "gauge-Higgs condition," we investigate the renormalization group evolution of the Higgs quartic coupling and find a relation between the bulk mass and the compactification scale so as to reproduce the 125 GeV Higgs boson mass. Through quantum corrections at the one-loop level, the bulk fermions contribute to the Higgs boson production and decay processes and deviate the Higgs boson signal strengths at the Large Hadron Collider (LHC) experiments from the Standard Model (SM) predictions. Employing the current experimental data which show the the Higgs boson signal strengths for a variety of Higgs decay modes are consistent with the SM predictions, we obtain lower mass bounds on the lightest mode of the bulk fermions.Show more Item Bosonic Description of Spinning Strings in 2 + 1 Dimensions(1996-09-15) Harms, B.; Stern, Allen; University of Alabama TuscaloosaShow more We write down a general action principle for spinning strings in (2+1)-dimensional space-time without introducing Grassmann variables. The action is written solely in terms of coordinates taking values in the 2+1 Poincaré group, and it has the usual string symmetries; i.e., it is invariant under (a) diffeomorphisms of the world sheet and (b) Poincaré transformations.Show more Item Bounds on large extra dimensions from the simulation of black hole events at the Large Hadron Collider(University of Alabama Libraries, 2016) Hou, Shaoqi; Harms, B.; University of Alabama TuscaloosaShow more Large extra dimensions were originally proposed to solve the hierarchy problem of the Standard Model (SM) of elementary particle physics. The presence of large extra dimensions dilutes gravity, lowering the Planck scale, while SM particles are required to propagate only in the usual 4 dimensional spacetime, leaving the electroweak scale unchanged. If large extra dimensions exist and they are large enough, the Planck scale may be as low as a few TeV’s, so that the hierarchy problem is solved. A smaller Planck scale will bring about numerous phenomenological consequences; in particular, microscopic black holes may be produced in high-energy particle collisions at this energy scale. The decay of black holes, via the Hawking effect, into elementary particles enables the detection of the black hole events, which can be used to infer the existence of large extra dimensions. In this work, we simulate microscopic black hole formation at the Large Hadron Collider with the black hole event generator CATFISH, and compare the simulation results with the experimental data published by the Compact Muon Solenoid collaboration in 2013 at a center of mass energy $\sqrt{s}= 8$ TeV, corresponding to an integrated luminosity of 12.1 fb$^{-1}$. The goal of this work is to test the large extra dimension model and to determine the value of the Planck scale if large extra dimensions exist. The absence of observed black hole events in the experimental data allows us to set lower bounds on the Planck scale and various parameters related to microscopic black hole formation for a number (3 - 6) of large extra dimensions. Assuming no energy loss during high-energy particle collisions, our analysis sets lower bounds on the fundamental Planck scale ranging from 0.8 TeV to 4.9 TeV for black holes fully decaying into SM particles and 0.5 TeV to 3.0 TeV for black holes settling down to a charge neutral, invisible remnant, depending on the minimum allowed black hole mass at formation. Formation of black holes with mass less than 5.2 TeV to 6.5 TeV (SM decay) and 2.2 TeV to 4.0 TeV (remnant) is excluded at 95\% C.L. Further investigation takes into account the effects of the Generalized Uncertainty Principle (GUP), which is expected to play an important role because the mass of a microscopic black hole is only a few fundamental Planck masses. An analysis similar to the one carried out without including GUP effects reveals smaller lower bounds on the fundamental Planck scale ranging from 0.8 TeV to 1.4 TeV for black holes fully decaying into SM particles, only when $\alpha\ge0.9$, depending on the minimum allowed black hole mass at formation. Therefore, this work constrains not only the sizes of the large extra dimensions and the masses of the microscopic black holes, but also sets the lower limits on the energy scale where the effects of quantum gravity start to become significant.Show more Item Collider phenomenology of heavy neutrinos(University of Alabama Libraries, 2016) Das, Arindam; Okada, Nobuchika; University of Alabama TuscaloosaShow more The existence of the neutrino mass has been established by the neutrino oscillation experiments. The so-called seesaw extension of the Standard Model is probably the simplest idea to naturally explain the existence of tiny neutrino mass through the lepton number violating Majorana mass term. There is another alternative way, commonly known as the inverse seesaw mechanism, where the small neutrino mass is obtained by the tiny lepton number violating parameters. In this work we investigate the signatures of such heavy neutrinos, having mass in the Electroweak scale at the high energy colliders. Based on a simple realization of inverse seesaw model we fix the model parameters to reproduce the neutrino oscillation data and to satisfy the other experimental constraints. We assume two flavor structures of the model and the different types of hierarchical light neutrino mass spectra. For completeness we consider the general parameterization for the model parameters by introducing an arbitrary orthogonal matrix and the nonzero Dirac and Majorana phases. Due to the smallness of the lepton number violating parameter this model can manifest the trilepton plus missing energy at the Large Hadron Collider(LHC). Using the recent LHC results for anomalous production of the multilepton events at $8$ TeV with a luminosity of $19.5$ fb$^{-1}$, we derive the direct upper bounds on the light-heavy neutrino mixing parameter as a function of the heavy neutrino mass. Using a variety of initial states such as quark-quark, quark-gluon and gluon-gluon as well as photon mediated processes for the Majorana heavy neutrinos we obtain direct upper bounds on the light-heavy neutrino mixing angles from the current LHC data at $8$ TeV. For the pseudo-Dirac heavy neutrinos produced from the various initial states using the recent anomalous multilepton search by the LHC at $8$ TeV with $19.5$ fb$^{-1}$ luminosity, we obtain upper bounds on the mixing angles.Show more Item Electrical studies on nickel ferrites and hybrid organic-inorganic semiconductors(University of Alabama Libraries, 2013) Hannan, Brian; LeClair, Patrick R.; University of Alabama TuscaloosaShow more Electrical characterization measurements are performed on ferrite samples and a hybrid organic-inorganic p-n junction. Impedance and resistivity measurements are performed to investigate conducting properties of nickel ferrite and their dependence on growth temperature, composition, and sample dimensions. Impedance measurements are performed on an organic-inorganic semiconductor device and is demonstrated to behave as a p-n junction for potential use in technological applications.Show more Item Gauged U(1) extension of the standard model and phenomenology(University of Alabama Libraries, 2018) Raut, Digesh; Okada, Nobuchika; University of Alabama TuscaloosaShow more Despite the tremendous success of the Standard Model (SM), it needs to be extended to explain the origin of cosmological inflation, dark matter (DM) and neutrino masses. We consider gauged U(1)x extended SM, where in addition to the SM particles, the model includes a U(1)x scalar, Z' gauge boson, and three generations of right-handed neutrinos (RHNs), where the U(1)x charges of all the particles are defined by a single free parameter xH. In this model context, we discuss the complementarity between the cosmological inflation, the DM physics, and new physics searches at the Large Hadron Colliders (LHC). With the identification of the U(1)x scalar as an inflaton field, we consider the cosmological inflation scenario. For an effective inflaton potential to develop an inflection-point with predictions consistent with cosmological observations, the mass ratios among the Z' boson, the RHNs, and the inflaton are fixed. Requiring the inflationary prediction to be consistent with the current cosmological observation and collider experimental results, we show that our scenario can be tested at the future collider experiments such as the High Luminosity-LHC and the SHiP experiment. We also consider SU(5) x U(1)x scenario, where the SU(5) grand unification of the SM quarks and leptons is realized for xH = -4/5. Hence, the U(1)x charge is quantized in this scenario. With an additional global Z-2 symmetry, one RHN, which is Z-2 odd particles, serves as the DM in the universe. We investigate the Z'-portal RHN DM scenario and find that the constraints from the DM relic abundance and the search results for a Z' boson resonance at the LHC Run-2 are complementary to narrow down the allowed parameter region, which will be fully covered by the future LHC experiments for the Z’ boson mass less than 5 TeV.Show more Item Growing hair on the extremal BTZ black hole(Elsevier, 2017-04-13) Harms, B.; Stern, A.; University of Alabama TuscaloosaShow more We show that the nonlinear a-model in an asymptotically AdS(3) space-time admits a novel local symmetry. The field action is assumed to be quartic in the nonlinear a-model fields and minimally coupled to gravity. The local symmetry transformation simultaneously twists the nonlinear a-model fields and changes the space-time metric, and it can be used to map the extremal BTZ black hole to infinitely many hairy black hole solutions. (C) 2017 The Authors. Published by Elsevier B.V. This is an open access article under the CC BY license.Show more Item Noncommutative Corrections to the Robertson-Walker Metric(2008-09-23) Fabi, S.; Harms, B.; Stern, Allen; University of Alabama TuscaloosaShow more Upon applying Chamseddine’s noncommutative deformation of gravity, we obtain the leading order noncommutative corrections to the Robertson-Walker metric tensor. We get an isotropic inhomogeneous metric tensor for a certain choice of the noncommutativity parameters. Moreover, the singularity of the commutative metric at t = 0 is replaced by a more involved space-time structure in the noncommutative theory. In a toy model we construct a scenario where there is no singularity at t = 0 at leading order in the noncommutativity parameter. Although singularities may still be present for nonzero t, they need not be the source of all timelike geodesics and the result resembles a bouncing cosmology.Show more Item Noncommutative geometry and matrix models(University of Alabama Libraries, 2017) Chaney, Andrea; Stern, Allen B.; University of Alabama TuscaloosaShow more Noncommutative geometry is a proposed description of spacetime at energies near or beyond the Planck scale. A particularly intriguing representation of a noncommutative algebra is the matrix representation. Matrix models have been shown to include geometry, gravity and nonperturbative aspects of string theory. We wish to use matrix models to study noncommutative aspects of cosmological models. We begin by studying a matrix model analog of the BTZ black hole, which is a solution of 2+1 general relativity. We propose a Chern-Simons type theory constructed from finite dimensional matrices. After introducing the notion of a rotationally invariant boundary, we count the degeneracy of physical degrees of freedom associated with the boundary. This number coincides with the number of degrees of freedom needed to reproduce the Bekenstein-Hawking entropy relation. Next we study rotationally invariant solutions to d dimensional matrix models. We find d-1 dimensional solutions which have desirable cosmological features, in particular, we find matrix models that resolve cosmological singularities. In the last section, we restrict our attention to a Lorentzian analog of the complex projective plane, which is a four-dimensional solution of an eight-dimensional matrix action.Show more Item Noncommutative spaces from matrix models(University of Alabama Libraries, 2016) Lu, Lei; Stern, Allen B.; University of Alabama TuscaloosaShow more Noncommutative (NC) spaces commonly arise as solutions to matrix model equations of motion. They are natural generalizations of the ordinary commutative spacetime. Such spaces may provide insights into physics close to the Planck scale, where quantum gravity becomes relevant. Although there has been much research in the literature, aspects of these NC spaces need further investigation. In this dissertation, we focus on properties of NC spaces in several different contexts. In particular, we study exact NC spaces which result from solutions to matrix model equations of motion. These spaces are associated with finite-dimensional Lie-algebras. More specifically, they are two-dimensional fuzzy spaces that arise from a three-dimensional Yang-Mills type matrix model, four-dimensional tensor-product fuzzy spaces from a tensorial matrix model, and Snyder algebra from a five-dimensional tensorial matrix model. In the first part of this dissertation, we study two-dimensional NC solutions to matrix equations of motion of extended IKKT-type matrix models in three-space-time dimensions. Perturbations around the NC solutions lead to NC field theories living on a two-dimensional space-time. The commutative limit of the solutions are smooth manifolds which can be associated with closed, open and static two-dimensional cosmologies. One particular solution is a Lorentzian fuzzy sphere, which leads to essentially a fuzzy sphere in the Minkowski space-time. In the commutative limit, this solution leads to an induced metric that does not have a fixed signature, and have a non-constant negative scalar curvature, along with singularities at two fixed latitudes. The singularities are absent in the matrix solution which provides a toy model for resolving the singularities of General relativity. We also discussed the two-dimensional fuzzy de Sitter space-time, which has irreducible representations of su(1,1) Lie-algebra in terms of principal, complementary and discrete series. Field theories on such backgrounds result from perturbations about the solutions. The perturbative analysis requires non-standard Seiberg-Witten maps which depend on the embeddings in the ambient space and the symplectic 2-form. We find interesting properties of the field theories in the commutative limit. For example, stability of the action may require adding symmetry breaking terms to the matrix action, along with a selected range for the matrix coefficients. In the second part of this dissertation, we study higher dimensional fuzzy spaces in a tensorial matrix model, which is a natural generalization to the three-dimensional actions and is valid in any number of space-time dimensions. Four-dimensional tensor product NC spaces can be constructed from two-dimensional NC spaces and may provide a setting for doing four-dimensional NC cosmology. Another solution to the tensorial matrix model equations of motion is the Snyder algebra. A crucial step in exploring NC physics is to understand the structure of the quantized space-time in terms of the group representations of the NC algebra. We therefore study the representation theory of the Snyder algebra and implementation of symmetry transformations on the resulted discrete lattices. We find the three-dimensional Snyder space to be associated with two distinct Hilbert spaces, which define two reducible representations of the su(2)*su(2) algebra. This implies the existence of two distinct lattice structures of Snyder space. The difference between the two representations is evident in the spectra of the position operators, which could only be integers in one case and half integers in the other case. We also show that despite the discrete nature of the Snyder space, continuous translations and rotations can be unitarily implemented on the lattices.Show more Item Spinning sigma-model solitons in 2+1 anti-de Sitter space(Elsevier, 2016-11-04) Harms, B.; Stern, A.; University of Alabama TuscaloosaShow more We obtain numerical solutions for rotating topological solitons of the nonlinear s-model in threedimensional anti-de Sitter space. Two types of solutions, i) and ii), are found. The s-model fields are everywhere well defined for both types of solutions, but they differ in their space-time domains. Any time slice of the space-time for the type i) solution has a causal singularity, despite the fact that all scalars constructed from the curvature tensor are bounded functions. No evidence of a horizon is seen for any of the solutions, and therefore the type i) solutions have naked singularities. On the other hand, the space-time domain, along with the fields, for the type ii) solutions are singularity free. Multiple families of solutions exhibiting bifurcation phenomena are found for this case. (C) 2016 The Authors. Published by Elsevier B.V.Show more Item Susy transitions in compact objects(University of Alabama Libraries, 2010) Perevalova, Irina A.; Clavelli, L.; University of Alabama TuscaloosaShow more From the very moment of discovery, gamma-ray bursts (GRB) became a very fascinating subject for study. Although this phenomena has been observed for four decades, the origin of such extraordinary events is yet to be discovered. In our research, we propose one possible explanation of the phenomena. We support our proposal with detailed theoretical calculations and computer simulations which give us confidence to consider the proposed model as consistent. The structure of the dissertation is the following: in the first chapter, after a brief introduction to the history of the GRB, we give a description of existing models of GRB origin, pointing out, however, the reasons why we cannot accept the models entirely. Then we give a review of the astronomical objects that will be important for our model. Finally in the end of the chapter we introduce our model. Chapter two is entirely theoretical. After a brief introduction of supersymmetry (SUSY) we provide the apparatus we used in later calculations. In chapter three we present the calculations for the fermion → s-fermion transition cross-sections for the Dirac sea and results of Monte Carlo simulations for these transitions. In chapter four we present different collective nuclear models and the results of numerical evaluations of the energy release during the SUSY transition. Energy balance for possible nuclear reactions is also provided in this chapter. Finally, we present our conclusions in chapter five.Show more