Spontaneous Twin Symmetry Breaking

We consider a twin Higgs scenario where the $Z_2$ twin symmetry is broken spontaneously, not explicitly. This scenario provides an interesting interpretation of the Higgs metastability in the standard model; the $SU(4)$ breaking scale $f$ is determined by the scale where the Higgs self quartic coupling flips its sign. However, for the misalignment of nonzero vacuum expectation values of the twin Higgs fields, parameter tuning of ${\cal O}(m_h^2/f^2)$ is required like explicit twin symmetry breaking scenarios. For the minimal model with the exact twin symmetry, $f$ is ${\cal O}$($10^{10}$ GeV), so the model is very unnatural. We point out that the tuning can be significantly reduced ($f\gtrsim 2.7$ TeV) if there are twin vector-like leptons with large Yukawa coupling to twin Higgs fields.Comment: 8 pages, 6 figures; published versio

Spectral Decomposition of Missing Transverse Energy at Hadron Colliders

We propose a spectral decomposition to systematically extract information of dark matter at hadron colliders. The differential cross section of events with missing transverse energy (MET) can be expressed by a linear combination of basis functions. In the case of $s$-channel mediator models for dark matter particle production, basis functions are identified with the differential cross sections of sub-processes of virtual mediator and visible particle production while the coefficients of basis functions correspond to dark matter invariant mass distribution in the manner of the K\"all\'en-Lehmann spectral decomposition. For a given MET data set and mediator model, we show that one can differentiate a certain dark matter-mediator interaction from another through spectral decomposition.Comment: 6+4 pages, 6 figures, PRL versio

Adiabatic Electroweak Baryogenesis Driven by an Axion-like Particle

An axion-like particle (ALP) offers a new direction in electroweak baryogenesis because the periodic nature enables it to trigger a strong first-order phase transition insensitively to the decay constant $f$. For $f$ much above TeV, the ALP-induced electroweak phase transition is approximately described by adiabatic processes, distinguishing our scenario for electroweak baryogenesis from the conventional ones. We show that, coupled to the electroweak anomaly, the ALP can naturally realize spontaneous electroweak baryogenesis to solve the matter-antimatter asymmetry problem for $f$ in the range between about $10^5$ GeV and $10^7$ GeV. In such an ALP window, the $CP$ violation for baryogenesis is totally free from the experimental constraints, especially from the recently improved limit on the electron electric dipole moment. Future searches for ALPs could probe our scenario while revealing the connection between electroweak symmetry breaking and baryogenesis.Comment: 12 pages, 5 figures, appendices added, published versio

Leptogenesis driven by majoron

We propose a leptogenesis scenario where baryon asymmetry generation is assisted by the kinetic motion of the majoron, $J$, in the process of lepton-number violating inverse decays of a right-handed neutrino, $N$. We investigate two distinct scenarios depending on the sources of majoron kinetic motion: 1) the misalignment mechanism, and 2) the kinetic misalignment mechanism. The former case can naturally generate the observed baryon asymmetry for the majoron mass $m_J \gtrsim \,{\rm TeV}$ and the right-handed neutrino's mass $M_{N} \gtrsim 10^{11}\,{\rm GeV}$. However, an additional decay channel of the majoron is required to avoid the overclosure problem of the majoron oscillation. The later scenario works successfully for $m_J \lesssim 100\,{\rm keV}$, and $M_{N} \lesssim 10^9\,{\rm GeV}$ while $M_N$ can be even far below the temperature of the electroweak phase transition as long as sufficiently large kinetic misalignment is provided. We also find that a sub-$100\,{\rm keV}$ majoron is a viable candidate for dark matter.Comment: 10 pages, 4 figure

125 GeV Higgs as a pseudo-Goldstone boson in supersymmetry with vector-like matters

We propose a possibility of the 125 GeV Higgs being a pseudo-Goldstone boson in supersymmetry with extra vector-like fermions. Higgs mass is obtained from loops of top quark and vector-like fermions from the global symmetry breaking scale f at around TeV. The mu, Bmu/mu \sim f are generated from the dynamics of global symmetry breaking and the Higgs quartic coupling vanishes at f as tan beta \simeq 1. The relation of msoft \sim $4\pi M_Z$ with f \sim mu \sim m_soft \sim TeV is obtained and large mu does not cause a fine tuning for the electroweak symmetry breaking. The Higgs to di-photon rate can be enhanced from the loop of uncolored vector-like matters. The stability problem of Higgs potential with vector-like fermions can be nicely cured by the UV completion with the Goldstone picture.Comment: 28 pages, 8 figure

Organization and Abstraction: The Architecture of Skidmore, Owings & Merrill from 1936 to 1956

This dissertation examines the history of the architecture firm, Skidmore, Owings & Merrill (SOM) between 1936 and 1956. While focusing on the birth and growth of SOM, this study attempts to position the firm in a larger historical development of the United States in the mid-twentieth century. While Louis Skidmore and Nathaniel A. Owings established the firm in 1936, the dissertation begins at the beginning of the Great Depression in 1929. During the 1930s, Skidmore and Owings learned critical lessons from industrial designers about the significance of the public as well as how to attract their attention. The founders discovered the importance of investigating people's reactions to certain forms and spaces, mainly working on small shops and exhibition halls. During WWII, SOM worked on prefabricated houses in the town of Oak Ridge, TN, which was part of the Manhattan Project. While working confidentially for the military for about three years, SOM mastered diverse kinds of building technology and gained experience with the various programs necessary for a conventional town. In addition, the firm constructed a modern architecture-engineering firm, which could handle complex architectural and engineering projects. As a result of their previous experience, SOM evolved into a leader in designing glass and steel office buildings after WWII, refining the architectural language it had discovered during the war. In the 1950s, the firm continued designing and constructing large town projects for American military and other corporations throughout the world. This dissertation records the shifts in the profession of architecture in each historical context throughout the mid-twentieth century. The first three chapters cover the years from 1929 to 1939, 1939 to 1945, and 1946 to 1956 respectively. The fourth chapter addresses the architecture community's perception of SOM and the firm's organizational characteristics. This dissertation investigates how SOM attempted to modernize architecture as a whole, responding to new materials as well as to the spatial and cultural conditions of the world

Dark matter filtering-out effect during a first-order phase transition

If the mass of dark matter is generated from a cosmological phase transition involving the nucleation of bubbles, the corresponding bubble walls can filter out dark matter particles during the phase transition. Only particles with sufficient momentum to overcome their mass inside the bubbles can pass through the walls. As a result, the dark matter number density after the phase transition has a suppression factor $\exp(-M_\chi/2\tilde \gamma T)$, where $M_\chi$ is the dark matter mass, and $\tilde \gamma$ and $T$ are the Lorentz factor and temperature of the incoming fluid in the bubble wall rest frame, respectively. Under certain assumptions, we show that the filtering-out process can naturally provide a large suppression consistent with the observed dark matter density for a wide range of dark matter masses up to the Planck scale. Since the first-order phase transition is the decisive ingredient in our mechanism, a new connection is made between heavy dark matter scenarios and gravitational wave observations.Comment: 6 pages, 2 figures, minor change, presentation improve

Dynamical mean-field theory of Hubbard-Holstein model at half-filling: Zero temperature metal-insulator and insulator-insulator transitions

We study the Hubbard-Holstein model, which includes both the electron-electron and electron-phonon interactions characterized by $U$ and $g$, respectively, employing the dynamical mean-field theory combined with Wilson's numerical renormalization group technique. A zero temperature phase diagram of metal-insulator and insulator-insulator transitions at half-filling is mapped out which exhibits the interplay between $U$ and $g$. As $U$ ($g$) is increased, a metal to Mott-Hubbard insulator (bipolaron insulator) transition occurs, and the two insulating states are distinct and can not be adiabatically connected. The nature of and transitions between the three states are discussed.Comment: 5 pages, 4 figures. Submitted to Physical Review Letter