We give a detailed analysis of the particle spectrum and the perturbative unitarity of the recently introduced Weyl-invariant version of the new massive gravity in $2+1$ dimensions. By computing the action up to second order in the fluctuations of the metric, the gauge and the scalar fields around the anti-de Sitter (AdS) and flat vacua, we find that the theory describes unitary (tachyon and ghost-free) massive spin-2, massive (or massless) spin-1 and massless spin-0 excitations for certain ranges of the dimensionless parameters. The theory is not unitary in de Sitter space. Scale invariance is either broken spontaneously (in AdS background) or radiatively (in flat background) and hence the masses of the particles are generated either spontaneously or at the second loop order.

A theory of position of massive bodies is proposed that results in an observable quantum behavior of geometry at the Planck scale, $t_P$. Departures from classical world lines in flat spacetime are described by Planckian noncommuting operators for position in different directions, as defined by interactions with null waves. The resulting evolution of position wave functions in two dimensions displays a new kind of directionally coherent quantum noise of transverse position. The amplitude of the effect in physical units is predicted with no parameters, by equating the number of degrees of freedom of position wave functions on a 2D space-like surface with the entropy density of a black hole event horizon of the same area. In a region of size $L$, the effect resembles spatially and directionally coherent random transverse shear deformations on time scale $\approx L/c$ with typical amplitude $\approx \sqrt{c{t}_{P}L}$. This quantum-geometrical “holographic noise” in position is not describable as fluctuations of a quantized metric, or as any kind of fluctuation, dispersion or propagation effect in quantum fields. In a Michelson interferometer the effect appears as noise that resembles a random Planckian walk of the beam splitter for durations up to the light-crossing time. Signal spectra and correlation functions in interferometers are derived, and predicted to be comparable with the sensitivities of current and planned experiments. It is proposed that nearly colocated Michelson interferometers of laboratory scale, cross-correlated at high frequency, can test the Planckian noise prediction with current technology.

We apply the monodromy method for the calculation of the functional determinant of a special second-order differential operator $\mathit{F}=-d^2/d{\tau }^2+\ddot{g}/g$, $\ddot{g}\equiv d^{2}g/d{\tau }^2$, subject to periodic boundary conditions with a periodic zero mode $g=g(\tau )$. This operator arises in applications of the early Universe theory and, in particular, determines the one-loop statistical sum for the microcanonical ensemble in cosmology generated by a conformal field theory (CFT). This ensemble realizes the concept of cosmological initial conditions by generalizing the notion of the no-boundary wave function of the Universe to the level of a special quasithermal state which is dominated by instantons with an oscillating scale factor of their Euclidean Friedmann-Robertson-Walker metric. These oscillations result in the multinode nature of the zero mode $g(\tau )$ of $\mathit{F}$, which is gauged out from its reduced functional determinant by the method of the Faddeev-Popov gauge-fixing procedure. The calculation is done for a general case of multiple nodes (roots) within the period range of the Euclidean time $\tau$, thus generalizing the previously known result for the single-node case of one oscillation of the cosmological scale factor. The functional determinant of $\mathit{F}$ expresses in terms of the monodromy of its basis function, which is obtained in quadratures as a sum of contributions of time segments connecting neighboring pairs of the zero mode roots within the period range.

The aim of the current work is a detailed time-series analysis of the data from dark matter direct detection experiments as well as related data sets. We examine recent claims that the cosmic ray muon flux can be responsible for generating the modulation signals seen by DAMA and, more recently, by the CoGeNT Collaboration. We find no evidence for such a strong correlation and show that the two phenomena differ in their power spectrum, phase, and possibly in amplitude. In addition, we investigate, in more detail, the time dependence of dark matter scattering. Since the signal is periodic with a period of a year (due to the Earth’s motion around the Sun), the presence of higher harmonics can be expected. We show that the higher harmonics generically have a similar phase to the annual modulation, and the biannual mode, in particular, could provide another handle in searching for dark matter in the laboratory.

We discuss a five-dimensional minimal supersymmetric standard model compactified on a $S^1/Z_2$ orbifold, looking at, in particular, the one-loop evolution equations of the Yukawa couplings for the quark sector and various flavor observables. Different possibilities for the matter fields are discussed; that is, where they are in the bulk or localized to the brane. The two possibilities give rise to quite different behaviors. By studying the implications of the evolution with the renormalization group of the Yukawa couplings and of the flavor observables, we find that, for a theory that is valid up to the unification scale, the case where fields are localized to the brane, with a large $\tan \beta$, would be more easily distinguishable from other scenarios.

Recent measurement of the $\gamma {\gamma }^{*}$ form factor of the neutral pion in the high $Q^2$ region disagrees with a priori predictions of QCD-based calculations. We comment on existing explanations, and analyze a possibility that this discrepancy is not due to poorly understood QCD effects, but is a result of some new physics beyond the standard model (SM). We show that such physics would necessarily involve a new neutral light state with mass close to the mass of ${\pi }^0$, and with stronger than ${\pi }^0$ couplings to heavier SM flavors such as $c$, $\tau$, and $b$. It is found that only the coupling to the $\tau$ lepton can survive the existing constraints and lead to the observed rise of the pion form factor relative to $Q^{-2}$ at high $Q^2$. We perform numerical fits to data and determine the allowed range of masses and couplings for such new particles. This range of masses and couplings could also reduce or eliminate the tension between the $e^{+}{e}^{-}$ and $\tau$ decay determinations of the hadronic vacuum polarization. Dedicated experimental analysis of $\tau$ pair production in association with such new states should provide a conclusive test of the new physics hypothesis as an explanation of the pion form factor rise. We also comment on the calculations of the pion form factor in the chiral quark model, and point out a possible dynamical origin of the quark mass scale inferred from the form factor measurement.

We present equations of motion for charged particles using balanced equations, and without introducing explicitly divergent quantities. This derivation contains as particular cases some well known equations of motion, as the Lorentz-Dirac equations. An study of our main equations in terms of order of the interaction with the external field conduces us to the Landau-Lifshitz equations. We find that the analysis in second order show a special behavior. We give an explicit presentation up to third order of our main equations, and expressions for the calculation of general orders.

I use the Nicolai map and ensuing (super)locality of appropriate correlation functions to prove the existence of an infinite number of degeneracies in the mass spectra and decay coupling constants in supersymmetric gluodynamics and its daughter orientifold theory at large $N$.

de Sitter symmetry on quantum level implies that operators describing a given system satisfy commutation relations of the de Sitter algebra. This approach gives a new perspective on fundamental notions of quantum theory. We discuss applications of the approach to the cosmological constant problem, gravity, and particle theory.

Two-point functions, mean-squared fluctuations, and the vacuum expectation value of the energy-momentum tensor operator are investigated for a massive scalar field with an arbitrary curvature coupling parameter, subject to a spherical boundary in the background of de Sitter spacetime. The field is prepared in the Bunch-Davies vacuum state and is constrained to satisfy Robin boundary conditions on the sphere. Both the interior and exterior regions are considered. For the calculation in the interior region, a mode-summation method is employed, supplemented with a variant of the generalized Abel-Plana formula. This allows us to explicitly extract the contributions to the expectation values which come from de Sitter spacetime without boundaries. We show that the vacuum energy-momentum tensor is nondiagonal, with the off-diagonal component corresponding to the energy flux along the radial direction. With dependence on the boundary condition and the mass of the field, this flux can be either positive or negative. Several limiting cases of interest are then studied. In terms of the curvature coupling parameter and the mass of the field, two very different regimes are realized, which exhibit monotonic and oscillatory behavior of the vacuum expectation values, respectively, far from the sphere. The decay of the boundary-induced expectation values at large distances from the sphere is shown to be a power-law decay (monotonic or oscillating), independent of the value of the field mass. The expressions for the Casimir densities in the exterior region are generalized for a more general class of spherically symmetric spacetimes inside the sphere.

We numerically solve the one-dimensional Boltzmann equation of the neutrino and antineutrino transport in accretion disks and obtain the fully energy-dependent and direction-dependent neutrino- and antineutrino-emitting spectra, under the condition that the distribution of the mass density, temperature and chemical components are given. Then, we apply the resulting neutrino- and antineutrino-emitting spectra to calculate the corresponding annihilation rate of neutrino pairs above the neutrino-dominated accretion disk and find that the released energy resulting from the annihilation of neutrino pairs cannot provide sufficient energy for the most energetic short gamma ray bursts whose isotropic luminosity can be as high as ${10}^{52}\mathrm{ergs}/\mathrm{s}$ unless the high-temperature zone, where the temperature is beyond 10 MeV, can stretch over 200 km in the disk. We also compare the resulting luminosity of neutrinos and antineutrinos with the results from the two commonly used approximate treatments of the neutrino and antineutrino luminosity: the Fermi-Dirac black-body limit and a simplified model of neutrino transport, i.e., the gray-body model, and find that both of them overestimate the neutrino/antineutrino luminosity and their annihilation rate greatly. Additionally, as did in Sawyer (2003), we also check the validity of the two-stream approximation, and find that it is a good approximation to high accuracy.

We derive the Layzer-Irvine equation in the presence of a homogeneous (or quasihomogeneous) dark energy component with an arbitrary equation of state. We extend the Layzer-Irvine equation to homogeneous and isotropic universes with an arbitrary number of dimensions and obtain the corresponding virial relation for sufficiently relaxed objects. We find analogous equations describing the dynamics of cosmic string loops and other p-branes of arbitrary dimensionality, discussing the corresponding relativistic and nonrelativistic limits. Finally, we generalize the Layzer-Irvine equation to account for a nonminimal interaction between dark matter and dark energy, discussing its practical use as a signature of such an interaction.

We examine cosmological, astrophysical and collider constraints on thermal dark matter (DM) with mass $m_X$ in the range $\sim 1\mathrm{MeV}–10\mathrm{GeV}$. Cosmic microwave background (CMB) observations, which severely constrain light symmetric DM, can be evaded if the DM relic density is sufficiently asymmetric. Cosmic microwave background constraints require the present anti-DM-to-DM ratio to be less than $\sim 2\times {10}^{-6}$ (${10}^{-1}$) for DM mass $m_X=1\mathrm{MeV}$ (10 GeV) with ionizing efficiency factor $f\sim 1$. We determine the minimum annihilation cross section for achieving these asymmetries subject to the relic density constraint; these cross sections are larger than the usual thermal annihilation cross section. On account of collider constraints, such annihilation cross sections can only be obtained by invoking light mediators. These light mediators can give rise to significant DM self-interactions, and we derive a lower bound on the mediator mass from elliptical DM halo shape constraints. We find that halo shapes require a mediator with mass $m_{\varphi }\gtrsim 4\times {10}^{-2}\mathrm{MeV}$ (40 MeV) for $m_X=1\mathrm{MeV}$ (10 GeV). We map all of these constraints to the parameter space of DM-electron and DM-nucleon scattering cross sections for direct detection. For DM-electron scattering, a significant fraction of the parameter space is already ruled out by beam-dump and supernova cooling constraints.

The VERITAS array of Cherenkov telescopes has carried out a deep observational program on the nearby dwarf spheroidal galaxy Segue 1. We report on the results of nearly 48 hours of good quality selected data, taken between January 2010 and May 2011. No significant $\gamma$-ray emission is detected at the nominal position of Segue 1, and upper limits on the integrated flux are derived. According to recent studies, Segue 1 is the most dark matter-dominated dwarf spheroidal galaxy currently known. We derive stringent bounds on various annihilating and decaying dark matter particle models. The upper limits on the velocity-weighted annihilation cross-section are $⟨\sigma v{⟩}^{95\%\mathrm{CL}}\lesssim {10}^{-23}{\mathrm{cm}}^3{\mathrm{s}}^{-1}$, improving our limits from previous observations of dwarf spheroidal galaxies by at least a factor of 2 for dark matter particle masses $m_{\chi }\gtrsim 300\mathrm{GeV}$. The lower limits on the decay lifetime are at the level of ${\tau }^{95\%\mathrm{CL}}\gtrsim {10}^{24}\mathrm{s}$. Finally, we address the interpretation of the cosmic ray lepton anomalies measured by ATIC and PAMELA in terms of dark matter annihilation, and show that the VERITAS observations of Segue 1 disfavor such a scenario.

We extend Douglas’ solution of the problem of finding minimal surfaces to anti-de Sitter space. The case of a circle as a boundary contour is elaborated. We discuss applications to $\mathcal{N}=4$ super Yang-Mills: a circular Wilson loop and the Schwinger process, where we calculate the $1/\sqrt{\lambda }$ correction to the critical value of constant electric field.

We present results from calculations of the orbital evolution in eccentric binaries of nonrotating black holes with extreme mass ratios. Our inspiral model is based on the method of osculating geodesics, and is the first to incorporate the full gravitational self-force (GSF) effect, including conservative corrections. The GSF information is encapsulated in an analytic interpolation formula based on numerical GSF data for over a thousand sample geodesic orbits. We assess the importance of including conservative GSF corrections in waveform models for gravitational-wave searches.

Recently, the ATLAS and CMS collaborations reported their search for a new heavy gauge boson $W^{\prime }$ with one lepton plus missing transverse momentum. We find that $W^{(2)}$, the second Kaluza-Klein (KK) state of the $W$ boson in the minimal universal extra dimension (mUED) model, can be a good candidate for this signal, as its branching ratio into $\ell \nu$ is sizable. Moreover, nearly degenerate KK mass spectra in the mUED model yield generically very soft standard model particles accompanying $W^{(2)}$ from the subsequent decays of the second KK quarks and gluons. In a hadron collider, this indirect $W^{(2)}$ production is difficult to distinguish from the $W^{(2)}$ single production. The involved strong interactions make it more important than the single production. The early LHC data on $\ell +{\mathrm{E̸}}_T$ signal for $1.1{\mathrm{fb}}^{-1}$ integrated luminosity is shown insufficient to limit our model. However, the results show that the present LHC $5.6{\mathrm{fb}}^{-1}$ data can cover most of the reasonable parameter space of the mUED model.

The technique of Weinberg’s spectral-function sum rule is a powerful tool for a study of models in which global symmetry is dynamically broken. It enables us to convert information on the short-distance behavior of a theory to relations among physical quantities which appear in the low-energy picture of the theory. We apply such technique to general supersymmetry breaking models to derive new sum rules.

The new MEG bound on $\mathrm{BR}(\mu \to e\gamma )$ provides the strongest upper bound on the scale of gauge mediation of supersymmetry breaking. If, in the future, this decay is observed by MEG, the mediation scale will become known to within 1 order of magnitude, and the seesaw scale will be constrained. In such a case, contributions from Planck mediated supersymmetry breaking are likely to be non-negligible, and an interpretation in terms of purely seesaw parameters will be impossible. The recent evidence for $|U_{e3}|\sim 0.15$ further sharpens the predictions of gauge-mediated supersymmetry breaking.

We present results on the chiral and deconfinement properties of the QCD transition at finite temperature. Calculations are performed with $2+1$ flavors of quarks using the p4, asqtad, and HISQ/tree actions. Lattices with temporal extent $N_{\tau }=6$, 8, and 12 are used to understand and control discretization errors and to reliably extrapolate estimates obtained at finite lattice spacings to the continuum limit. The chiral transition temperature is defined in terms of the phase transition in a theory with two massless flavors and analyzed using $O(N)$ scaling fits to the chiral condensate and susceptibility. We find consistent estimates from the HISQ/tree and asqtad actions and our main result is $T_c=154\pm 9\mathrm{MeV}$.