17997328
Diffuse gamma-ray background and primordial black hole constraints on the spectral index of density fluctuations
We calculate the flux of $\ensuremath{\gamma}$ rays emitted from primordial black holes (PBHs) which are formed by a ``blue'' power-law spectrum of density fluctuations in the early universe. Gamma-ray emission from such PBHs may contribute significantly to the observed extragalactic diffuse $\ensuremath{\gamma}$-ray background (DGB). Using the observed DGB flux from the imaging Compton Telescope (COMPTEL) and the Energetic Gamma Ray Experiment Telescope (EGRET) as the upper limit of $\ensuremath{\gamma}$-ray flux from PBHs, we derive the upper limit on the spectral index n of the density fluctuations. The range of initial PBH masses which can contribute to the DGB is $2\ifmmode\times\else\texttimes\fi{}{10}^{13} \mathrm{g}\ensuremath{-}5\ifmmode\times\else\texttimes\fi{}{10}^{14} \mathrm{g},$ corresponding to a cosmic reheating temperature of $7\ifmmode\times\else\texttimes\fi{}{10}^{7} \mathrm{GeV}\ensuremath{-}4\ifmmode\times\else\texttimes\fi{}{10}^{8} \mathrm{GeV}.$ In this range, we find the upper limit to be $n\ensuremath{\lesssim}1.23\ensuremath{-}1.25.$ This limit is stronger than those derived from the energy density in PBHs or PBH relics and matches the value of n required to explain the cosmic microwave background anisotropy.
16162020
Boson Stars with Self-Interacting Quantum Scalar Fields
The Klein-Gordon-Einstein equations of classical real scalar fields have time-dependent solutions (periodic in time). We show that quantum real scalar fields can form non-oscillating (static) solitonic objects, which are quite similar to the solutions describing boson stars formed with classical and quantum complex scalar fields (the latter will be studied in this paper). We numerically analyze the difference between them concerning the mass of boson stars. On the other hand, we suggest an interesting test (a viable process that the boson star may undergo in the early universe) for the formation of boson stars. That is, it is questioned that after a second-order phase transition (a simple toy model will be considered here), what is the fate of the boson star composed of quantum real scalar field.
1893865
Black-string solutions with arbitrary tension
We consider 1+4 dimensional black-string solutions which are invariant under translation along the fifth direction. The solutions are characterized by the two parameters, mass and tension, of the source. The Gregory-Laflamme solution is shown to be characterized by the tension whose magnitude is one half of the mass per unit length of the source. A general class of black-string solutions with arbitrary tension is presented and the spacetime properties of the solutions are discussed.
2929156
Relativistic Electrodynamics of Spinning Compact Objects
A theoretical study of some electrodynamic features of a region close to a slowly-rotating magnetized relativistic star is performed. To be a little more specific, based on the solution-generating method given by Wald, the magnetic fields around both uncharged and (slightly) charged relativistic stars have been obtained. Particularly for a charged relativistic star, again following the argument by Wald, the star was shown to gradually accrete charge until it reached an equilibrium value Q = 2B0J . This value of the equilibrium charge seems to be generic as a rotating black hole is known to accrete exactly the same amount. Although these results are equally relevant to all species of slowly-rotating relativistic stars, we particularly have the rotating neutron star in mind. As such, it would be of some interest to attempt to make contact with a real pulsar case. Thus, we discuss how many of the theoretical results obtained in the present work can be carried over to a realistic, general relativistic description of a pulsar’s magnetosphere.
117905421
The nucleation of false vacuum bubbles with compact geometries
We investigate and classify the possible types of false vacuum bubbles in Einstein gravity. The false vacuum bubbles can occur only if gravity is taken into account. We show that there exist solutions only with compact geometries. The analytic computations for the radius and nucleation rate of a vacuum bubble are evaluated using the thin-wall approximation. We discuss possible cosmological implications of our new solutions.
5695541
Nonvanishing magnetic flux through the slightly charged Kerr black hole
In association with the Blanford-Znajek mechanism for rotational energy extraction from Kerr black holes, it is of some interest to explore how much of magnetic flux can actually penetrate the horizon at least in idealized situations. For completely uncharged Kerr hole case, it has been known for some time that the magnetic flux gets entirely expelled when the hole is maximally-rotating. In the mean time, it is known that when the rotating hole is immersed in an originally uniform magnetic field surrounded by an ionized interstellar medium (plasma), which is a more realistic situation, the hole accretes certain amount of electric charge. In the present work, it is demonstrated that as a result of this accretion charge small enough not to disturb the geometry, the magnetic flux through this slightly charged Kerr hole depends not only on the hole's angular momentum but on the hole's charge as well such that it never vanishes for any value of the hole's angular momentum.
55074643
Speculative Reading, Speculative Physics - the Ontology of the Large Hadron Collider
The objective is to illustrate the hermeneutics of reading against the highly image-dependent (rather than object-oriented) world of experimental particle physics. Reading becomes the medium for mediating between the real and the virtual when constructing physical knowledge. "Virtual" particles, produced through material inter-course between machine and nature, are productive for re- thinking the virtual/real entanglement. Reading enables a process of deconstructing and re-naturalizing microphysical trails, objects, and movements 'transformed' into machine code, post-detector. The process of reading is therefore the 'detection,' 'observation,' 'measurement,' 'abduction,' and 'interpretation' of coded information and knowledge; deciphered through data 'selected' for analysis, extrapolated as evidence for the confirmation/re-orientation of theoretical predictions, and included for the re-envisioning and revising of foundational explanations regarding the structure of modern physics. Reading as is explored here is about how reading as an act is inextricably linked with understanding one's perspective and the ideology one is immersed in, thus influencing how discovery is made and articulated through theory-construction.
119269079
Double non-global logarithms in-n-out of jets
A bstractWe derive the leading non-global logarithms (NGLs) of ratios of jet masses m1,2 and a jet energy veto Λ due to soft gluons splitting into regions in and out of jets. Such NGLs appear in any exclusive jet cross section with multiple jet measurements or with a veto imposed on additional jets. Here, we consider back-to-back jets of radius R produced in e+e− collisions, found with a cone or recombination algorithm. The leading NGLs are of the form $\alpha_{\text{s}}^2{\text{l}}{{\text{n}}^2}(\Lambda /{m_{{1},{2}}})$ or $\alpha_{\text{s}}^2{\text{l}}{{\text{n}}^2}({m_1}/{m_2})$. Their coefficients depend both on the algorithm and on R. We consider cone, kT, anti-kT, and Cambridge-Aachen algorithms. In addition to determining the full algorithmic and R dependence of the leading NGLs, we derive new relations among their coefficients. We also derive to all orders in αs a factorized form for the soft function S(kL, kR, Λ) in the cross section σ(m1, m2, Λ) in which dependence on each of the global logs of μ/kL, μ/kR and μ/Λ determined by the renormalization group are separated from one another and from the non-global logs. The same kind of soft function, its associated non-global structure, and the algorithmic dependence we derive here will also arise in exclusive jet cross sections at hadron colliders, and must be understood and brought under control to achieve precise theoretical predictions.
2435715
Late time behaviors of an inhomogeneous rolling tachyon
We study an inhomogeneous decay of an unstable D-brane in the context of Dirac-Born-Infeld (DBI)-type effective action. We consider tachyon and electromagnetic fields with dependence of time and one spatial coordinate, and an exact solution is found under an exponentially decreasing tachyon potential, e{sup -|T|/{radical}}{sup (2)}, which is valid for the description of the late time behavior of an unstable D-brane. Though the obtained solution contains both time and spatial dependence, the corresponding momentum density vanishes over the entire spacetime region. The solution is governed by two parameters. One adjusts the distribution of energy density in the inhomogeneous direction, and the other interpolates between the homogeneous rolling tachyon and static configuration. As time evolves, the energy of the unstable D-brane is converted into the electric flux and tachyon matter.
119515668
Probing Physics in the Standard Model and Beyond with Electroweak Baryogenesis and Effective Theories of the Strong Interactions
We address in this thesis two primary questions aimed at improving our ability to calculate reliably in the Standard Model of particle physics and probing possible new particles which may exist beyond it. 
 
First, we embark on an attempt to account for the abundance of matter in the present Universe if earlier in its history matter and antimatter were equally abundant. We explore whether baryogenesis at the electroweak phase transition could successfully account for the observed density of baryons in the Universe, using the closed-time-path (CTP) formalism of quantum field theory to calculate the buildup and relaxation of particle densities during the phase transition. For our model of the new particles and sources of CP violation necessary to account for the baryon asymmetry of the Universe, we adopt the Minimal Supersymmetric Extension of the Standard Model (MSSM). We look for regions of the parameter space in the MSSM that could give rise to sufficiently large baryon asymmetry without violating constraints on these parameters from existing experiments, in particular, constraints on masses of Higgs and supersymmetric particles from accelerator searches and precision electroweak tests, and on CP-violating parameters of the MSSM from searches for electric dipole moments of elementary particles. 
 
Next, we explore how to get around our ignorance of the dynamics of strongly interacting particles in the nonperturbative regime of Quantum Chromodynamics (QCD) by the clever use of effective field theories. Two applications are explored: the decay of Z bosons to hadronic jets using soft-collinear effective theory (SCET) and the radiative decays of quarkonia to light hadrons using SCET and non-relativistic QCD (NRQCD). These tools facilitate the proof of factorization of decay rates into perturbatively-calculable and nonperturbative parts. Universality of the latter among different observables provides predictive power even in our ignorance of the details of the nonperturbative physics.
17502138
Probing the Structure of Jets: Factorized and Resummed Angularity Distributions in SCET
Using the framework of soft-collinear effective theory (SCET), we factorize and calculate $e^+e^-$ angularity distributions, including perturbative resummation and the incorporation of a universal model for the nonperturbative soft function. Angularities $\tau_a$ are a class of event shapes varying in their sensitivity to the substructure of jets in the final state, controlled by a continuous parameter $a<2$. We calculate the jet and soft functions in factorized angularity distributions for all $a<1$ to first order in the strong coupling $\alpha_s$ and resum large logarithms to next-to-leading logarithmic (NLL) accuracy. We employ a universal model for the nonperturbative soft function with a gap parameter which cancels the renormalon ambiguity in the partonic soft function.