We investigate singular geometries which can be associated with warped branes in arbitrary dimensions. If the brane tension is allowed to be variable, the extremum condition for the action requires additional constraints beyond the solution of the field equations. In a higher-dimensional world, such constraints arise from variations of the metric which are local in the usual four-dimensional space-time, without changing the geometry of internal space. As a consequence, continuous families of singular solutions of the field equations, with arbitrary integration constants, are generically reduced to a discrete subset of extrema of the action, similar to regular spaces. As an example, previously found static solutions of six-dimensional gravity with a cosmological constant, that lead to effective four-dimensional gravity, are not extrema of the action. These findings explain why the field equations of the reduced four-dimensional theory are not generically consistent with arbitrary solutions of the higher-dimensional field equations—consistency requires the additional constraints. Characteristic solutions for variable tension branes are nonstatic runaway solutions where the effective four-dimensional cosmological constant vanishes as time goes to infinity.

We investigate the Affleck-Dine mechanism when multiple flat directions simultaneously have large values. We consider in detail the case when both the $L{H}_u$ and the $H_u{H}_d$ flat directions are operative with a nonrenormalizable superpotential. In the case where Hubble induced $A$ terms are present for these two flat directions, their initial values are determined completely by the potential and there are no ambiguities in how they are mixed. Moreover, $CP$ is violated even when the Hubble parameter is large due to the Hubble induced $A$ term and a cross coupling of the $F$ term, so that the lepton asymmetry is generated just after the end of inflation. As a result, compared with the case of a single flat direction, the resultant lepton-to-entropy ratio is enhanced by a factor of $H_{\mathrm{osc}}/m_{3/2}$, where $H_{\mathrm{osc}}$ is the Hubble parameter at the onset of oscillation of the flat direction and $m_{3/2}$ is the gravitino mass. However, when the Hubble induced $A$ terms do not exist, there remains indefiniteness of initial phases and $CP$ is violated spontaneously by the phase difference between the initial phases and the points of the minima of the hidden-sector induced $A$ terms. Therefore, $CP$ violation is not effective until the onset of the oscillation of the scalar fields around the origin and there is a suppression factor from thermal effects as in the case of a single flat direction. In this case, the amplitude of baryon isocurvature perturbations imposes constraints on the model parameters.

In this work we develop a new propagation model for the Galactic cosmic rays based on the GALPROP code, including contributions from dark matter annihilation. Its predictions of the Galactic diffuse $\gamma$-ray spectra are compatible with the EGRET data in all sky regions. It also gives consistent results about the diffuse $\gamma$ ray longitude and latitude distributions. The $\mathrm{B}/\mathrm{C}$, ${}^{10}\mathrm{Be}/{}^9\mathrm{Be}$, proton, electron and antiproton spectra are in agreement with cosmic ray measurements as well. In this model we have taken a universal proton spectrum throughout the Galaxy without introducing large fluctuation, considering the proton energy loss is negligible. The dark matter annihilation signals are boosted after taking the contributions from subhalos into account. Another interesting feature of this model is that it gives a better description of the diffuse $\gamma$ rays when taking the source distribution compatible with supernova remnants data, which is different from previous studies.

Phase transitions in the imaginary chemical potential region are studied by the Polyakov-loop extended Nambu–Jona-Lasinio model that possesses the extended ${\mathbb{Z}}_3$ symmetry. The extended-${\mathbb{Z}}_3$ invariant quantities such as the partition function, the chiral condensate, and the modified Polyakov loop have the Roberge-Weiss (RW) periodicity. There appear four types of phase transitions: deconfinement, chiral, Polyakov-loop RW, and chiral RW transitions. The orders of the chiral and deconfinement transitions depend on the presence or absence of current quark mass, but those of the Polyakov-loop RW and chiral RW transitions do not. The scalar-type, eight-quark interaction newly added in the model makes the chiral transition line shift to the vicinity of the deconfinement transition line.

We extend to larger unification groups an earlier study exploring the possibility of unification of gauge symmetries in theories with dynamical symmetry breaking. Based on our results, we comment on the outlook for models that seek to achieve this type of unification.

In any theory it is unnatural if the observed values of parameters lie very close to special values that determine the existence of complex structures necessary for observers. A naturalness probability $P$ is introduced to numerically evaluate the degree of unnaturalness. If $P$ is very small in all known theories, corresponding to a high degree of fine-tuning, then there is an observer naturalness problem. In addition to the well-known case of the cosmological constant, we argue that nuclear stability and electroweak symmetry breaking represent significant observer naturalness problems. The naturalness probability associated with nuclear stability depends on the theory of flavor, but for all known theories is conservatively estimated as $P_{\mathrm{nuc}}\lesssim ({10}^{-3}–{10}^{-2})$, and for simple theories of electroweak symmetry breaking $P_{\mathrm{EWSB}}\lesssim ({10}^{-2}–{10}^{-1})$. This pattern of unnaturalness in three different arenas, cosmology, nuclear physics, and electroweak symmetry breaking, provides evidence for the multiverse, since each problem may be easily solved by environmental selection. In the nuclear case the problem is largely solved even if the multiverse distribution for the relevant parameters is relatively flat. With somewhat strongly varying distributions, it is possible to understand both the close proximity to neutron stability and the values of $m_e$ and $m_d-m_u$ in terms of the electromagnetic mass difference between the proton and neutron, ${\delta }_{\mathrm{EM}}\simeq 1\pm 0.5\mathrm{MeV}$. It is reasonable that multiverse distributions are strong functions of Lagrangian parameters, since they depend not only on the landscape of vacua, but also on the population mechanism, “integrating out” other parameters, and on a density of observers factor. In any theory with mass scale $M$ that is the origin of electroweak symmetry breaking, strongly varying multiverse distributions typically lead either to a little hierarchy $v/M\approx ({10}^{-2}–{10}^{-1})$, or to a large hierarchy $v\ll M$. In certain multiverses, where electroweak symmetry breaking occurs only if $M$ is below some critical value, we find that a little hierarchy develops with the value of $v^2/M^2$ suppressed by an extra loop factor, as well as by the strength of the distribution. Since the correct theory of electroweak symmetry breaking is unknown, our estimate for $P_{\mathrm{EWSB}}$ is theoretical. The LHC will lead to a much more robust determination of $P_{\mathrm{EWSB}}$, and, depending on which theory is indicated by the data, the observer naturalness problem of electroweak symmetry breaking may be removed or strengthened. For each of the three arenas, the discovery of a natural theory would eliminate the evidence for the multiverse; but in the absence of such a theory, the multiverse provides a provisional understanding of the data.

We show that in the framework of the teleparallel equivalent of general relativity the gravitational energy-momentum of plane-fronted gravitational waves contained in an arbitrary three-dimensional volume $V$ may be easily obtained and is non-negative in the frame of static observers.

We study the stellar magnetic field configuration in dependence on brane tension and present solutions of Maxwell equations in the external background space-time of a magnetized spherical star in a Randall-Sundrum II type braneworld. The star is modeled as a sphere consisting of perfect highly magnetized fluid with infinite conductivity and a frozen-in magnetic field. With respect to solutions for magnetic fields found in the Schwarzschild space-time, brane tension introduces enhancing corrections to the exterior magnetic field which could be relevant for the magnetic fields of magnetized compact objects as pulsars and magnetars and may provide observational evidence for the brane tension.

We shall consider a 3-brane embedded in six-dimensional space-time with a negative bulk cosmological constant. The 3-brane is constructed by a topological soliton solution living in two-dimensional axially symmetric transverse subspace. Similar to most previous works of six-dimensional soliton models, our Maxwell gauged $\mathbb{C}{P}^1$ brane model can also achieve localizing gravity around the 3-brane. The $\mathbb{C}{P}^1$ field is described by a scalar doublet and derived from the $O(3)$ sigma model by projecting it onto two-dimensional complex space. In that sense, our framework is more effective than other solitonic brane models concerning gauge theory. We shall also discuss the linear stability analysis for our new model by fluctuating all fields.

We provide a compact analytic formula to compute the spin of the black hole produced by the coalescence of two black holes following a quasicircular inspiral. Without additional fits than those already available for binaries with aligned or antialigned spins, but with a minimal set of assumptions, we derive an expression that can model generic initial spin configurations and mass ratios, thus covering all of the 7-dimensional space of parameters. A comparison with simulations already shows very accurate agreements with all of the numerical data available to date, but we also suggest a number of ways in which our predictions can be further improved.

We consider free and self-interacting quantum scalar fields satisfying modified dispersion relations in the framework of Einstein-Aether theory. Using adiabatic regularization, we study the renormalization of the equation for the mean value of the field in the self-interacting case, and the renormalization of the semiclassical Einstein-Aether equations for free fields. In both cases we consider Bianchi type I background spacetimes. Contrary to what happens for free fields in flat Robertson-Walker spacetimes, the self-interaction and/or the anisotropy produce nonpurely geometric terms in the adiabatic expansion, i.e. terms that involve both the metric $g_{\mu \nu }$ and the aether field $u_{\mu }$. We argue that, in a general spacetime, the renormalization of the theory would involve new counterterms constructed with $g_{\mu \nu }$ and $u_{\mu }$, generating a fine-tuning problem for the Einstein-Aether theory.

I propose a new volume-weighted probability measure for cosmological “multiverse” scenarios involving eternal inflation. The “reheating-volume (RV) cutoff” calculates the distribution of observable quantities on a portion of the reheating hypersurface that is conditioned to be finite. The RV measure is gauge-invariant, does not suffer from the “youngness paradox,” and is independent of initial conditions at the beginning of inflation. In slow-roll inflationary models with a scalar inflaton, the RV-regulated probability distributions can be obtained by solving nonlinear diffusion equations. I discuss possible applications of the new measure to “landscape” scenarios with bubble nucleation. As an illustration, I compute the predictions of the RV measure in a simple toy landscape.

We propose a new method of searching for the composition-dependent dilatonic waves, predicted by unified theories of strings. In this method, Earth’s surface-gravity changes due to translational motions of its inner core, excited by dilatonic waves, are searched for by using superconducting gravimeters. This method has its best sensitivity at the frequency of $\sim 7\times {10}^{-5}\mathrm{Hz}$, which is lower than the sensitive frequencies of previous proposals using gravitational wave detectors: $\sim 10$ to 1000 Hz. Using available results of surface-gravity measurements with superconducting gravimeters and assuming a simple Earth model, we present preliminary upper limits on the energy density of a stochastic background of massless dilatons at the low frequency. Though the results are currently limited by the uncertainty in the Earth model, this method has a potential of detecting dilatonic waves in a new window.

We have used the light-cone formulation of the chiral-quark soliton model to investigate the vector and axial content of octet, decuplet, and hypothetical antidecuplet in the flavor $SU(3)$ symmetry limit. We have extended previous works by computing the $7Q$ contribution to vector and axial charges for the octet and antidecuplet but stayed at the $5Q$ sector for the decuplet where the full computation needs much more time. As expected, the $7Q$ component has a weaker impact on the quantities but still changes them by a few percent. We give also a detailed decomposition of those charges into flavor, valence quark, sea quark, and antiquark contributions. Many of them are of course not (yet) measured or estimated and constitute then a theoretical estimation. Among the different interesting observations made in this work are the explicit quadrupole deformation of decuplet baryons due to the pion field and the sum of quark spins larger than the pentaquark one.

Understanding the finite-size corrections to the fundamental excitations of a theory is the first step towards completely solving for the spectrum in finite volume. We compute the leading exponential correction to the quantum energy of the fundamental excitation of the light-cone gauged string in ${\mathrm{AdS}}_5\times S^5$, which is the giant magnon solution. We present two independent ways to obtain this correction: the first approach makes use of the algebraic curve description of the giant magnon. The second relies on the purely field-theoretical Lüscher formulas, which depend on the world-sheet$S$-matrix. We demonstrate the agreement to all orders in $(\Delta /\sqrt{\lambda }{)}^{-1}$ of these approaches, which, in particular, presents a further test of the $S$-matrix. We comment on generalizations of this method of computation to other string configurations.

Light-front holography is a remarkable feature of the AdS/CFT correspondence between gravity in AdS space and conformal field theories in physical space-time; it allows string modes $\Phi (z)$ in the anti-de Sitter (AdS) fifth dimension to be precisely mapped to the light-front wave functions of hadrons in physical space-time in terms of a specific light-front impact variable $\zeta$ which measures the separation of the quark and gluonic constituents within the hadron. This mapping was originally obtained by matching the exact expression for electromagnetic current matrix elements in AdS space with the corresponding exact expression for the current matrix element using light-front theory in physical space-time. In this paper we show that one obtains the identical holographic mapping using matrix elements of the energy-momentum tensor. To prove this, we show that there exists a correspondence between the matrix elements of the energy-momentum tensor of the fundamental hadronic constituents in QCD with the transition amplitudes describing the interaction of string modes in AdS space with an external graviton field which propagates in the AdS interior. The agreement of the results for electromagnetic and gravitational hadronic transition amplitudes provides an important consistency test and verification of holographic mapping from AdS to physical observables defined on the light front.

We investigated the noise of interferometric gravitational wave detectors due to heat energy deposited by cosmic-ray particles. We derived a general formula that describes the response of a mirror against a cosmic-ray passage. We found that there are differences in the comic-ray responses (the dependence of temperature and cosmic-ray track position) in cases of interferometric and resonant gravitational wave detectors. The power spectral density of vibrations caused by low-energy secondary muons is 100 times smaller than the goal sensitivity of future second-generation interferometer projects, such as LCGT and Advanced LIGO. The arrival frequency of high-energy cosmic-ray muons that generate enough large showers inside mirrors of LCGT and Advanced LIGO is one per a millennium. We also discuss the probability of exotic-particle detection with interferometers.

We study equilibrium conditions between a static, spherically symmetric black hole and classical matter in terms of the radial pressure to density ratio $p_r/\rho =w(u)$, where $u$ is the radial coordinate. It is shown that such an equilibrium is possible in two cases: (i) the well-known case $w\to -1$ as $u\to u_h$ (the horizon), i.e., “vacuum” matter, for which $\rho (u_h)$ can be nonzero; (ii) $w\to -1/(1+2k)$ and $\rho \sim (u-u_h{)}^k$ as $u\to u_h$, where $k>0$ is a positive integer ($w=-1/3$ in the generic case $k=1$). A noninteracting mixture of these two kinds of matter can also exist. The whole reasoning is local, hence the results do not depend on any global or asymptotic conditions. They mean, in particular, that a static black hole cannot live inside a star with nonnegative pressure and density. As an example, an exact solution for an isotropic fluid with $w=-1/3$ (that is, a fluid of disordered cosmic strings), with or without vacuum matter, is presented.

We study the complete $\mathcal{O}({\alpha }_{\mathrm{ew}})$ electroweak (EW) corrections to the production of three $Z^0$ bosons in the framework of the standard model (SM) at the ILC. The leading-order and the EW next-to-leading-order corrected cross sections are presented, and their dependence on the colliding energy $\sqrt{s}$ and Higgs-boson mass $m_H$ is analyzed. We investigate also the LO and one-loop EW corrected distributions of the transverse momentum of the final $Z^0$ boson, and the invariant mass of the $Z^0{Z}^0$ pair. Our numerical results show that the EW one-loop correction generally suppresses the tree-level cross section, and the relative correction with $m_H=120\mathrm{GeV}(150\mathrm{GeV})$ varies between $-15.8\%(-13.9\%)$ and $-7.5\%(-6.2\%)$ when $\sqrt{s}$ goes up from 350 GeV to 1 TeV.