We investigate spontaneous symmetry breaking in Lorentz-noninvariant theories. Our general discussion includes relativistic systems at finite density as well as intrinsically nonrelativistic systems. The main result of the paper is a direct proof that nonzero density of a non-Abelian charge in the ground state implies the existence of a Goldstone boson with nonlinear (typically, quadratic) dispersion law. We show that the Goldstone boson dispersion relation may in general be extracted from the current transition amplitude and demonstrate on examples from recent literature, how the calculation of the dispersion relation is utilized by this method. After then, we use the general results to analyze the nonrelativistic degenerate Fermi gas of four fermion species. Because of its internal SU(4) symmetry, this system provides an analog to relativistic two-color quantum chromodynamics with two quark flavors. In the end, we extend our results to pseudo-Goldstone bosons of an explicitly broken symmetry.

We study Cerenkov radiation from moving straight strings which slide with respect to each other in such a way that the projected intersection point moves faster than light. To calculate this effect we develop classical perturbation theory for the system of Nambu-Goto strings interacting with the dilaton, two-form, and gravity fields. In the first order, one encounters divergent self-action terms which are eliminated by classical renormalization of the string tension. Cerenkov radiation arises in the second order. It is generated by an effective source which contains contributions localized on the string world sheets and bulk contributions quadratic in the first-order fields. In the ultrarelativistic limit radiation exhibits angular peaking on the Cerenkov cone in the forward direction of the fast string in the rest frame of another. The radiation spectrum then extends up to high frequencies proportional to the square of the Lorentz factor of the relative velocity. Gravitational radiation is absent since the $1+2$ space-time transverse to the straight string does not allow for gravitons. A rough estimate of the Cerenkov radiation in the cosmological cosmic strings network is presented.

Observed data are often contaminated by undiscovered interlopers, leading to biased parameter estimation. Here we present BEAMS (Bayesian estimation applied to multiple species) which significantly improves on the standard maximum likelihood approach in the case where the probability for each data point being “pure” is known. We discuss the application of BEAMS to future type-Ia supernovae (SNIa) surveys, such as LSST, which are projected to deliver over a million supernovae light curves without spectra. The multiband light curves for each candidate will provide a probability of being Ia (pure) but the full sample will be significantly contaminated with other types of supernovae and transients. Given a sample of $N$ supernovae with mean probability, $⟨P⟩$, of being Ia, BEAMS delivers parameter constraints equal to $N⟨P⟩$ spectroscopically confirmed SNIa. In addition BEAMS can be simultaneously used to tease apart different families of data and to recover properties of the underlying distributions of those families (e.g. the type-Ibc and II distributions). Hence BEAMS provides a unified classification and parameter estimation methodology which may be useful in a diverse range of problems such as photometric redshift estimation or, indeed, any parameter estimation problem where contamination is an issue.

We propose a brane configuration for the $(2+1)\mathrm{d}$, $\mathcal{N}=2$ superconformal theories (${\mathrm{CFT}}_3$) arising from M2 branes probing toric Calabi-Yau 4-fold cones, using a T-duality transformation of M theory. We obtain intersections of M5-branes on a three-torus which form a 3d bipartite crystal lattice in a way similar to the 2d dimer models for ${\mathrm{CFT}}_4$. The fundamental fields of the ${\mathrm{CFT}}_3$ are M2-brane discs localized around the intersections, and the superpotential terms are identified with the atoms of the crystal. The model correctly reproduces the Bogomol’nyi-Prasad-Sommerfield (BPS) spectrum of mesons.

We show that any Lorentz-violating theory with two or more propagation speeds is in conflict with the generalized second law of black hole thermodynamics. We do this by identifying a classical energy-extraction method, analogous to the Penrose process, which would decrease the black hole entropy. Although the usual definitions of black hole entropy are ambiguous in this context, we require only very mild assumptions about its dependence on the mass. This extends the result found by Dubovsky and Sibiryakov, which uses the Hawking effect and applies only if the fields with different propagation speeds interact just through gravity. We also point out instabilities that could interfere with their black hole perpetuum mobile, but argue that these can be neglected if the black hole mass is sufficiently large.

In the Randall-Sundrum model, we study top-antitop pair production and top spin correlations at the Large Hadron Collider. In addition to the standard model processes, there is a new contribution to the top-antitop pair production process mediated by graviton Kaluza-Klein modes in the $s$-channel. We calculate the density matrix for the top-antitop pair production including the new contribution. With a reasonable parameter choice in the Randall-Sundrum model, we find a sizable deviation of the top-antitop pair production cross section and the top spin correlations from those in the standard model. In particular, resonant productions of the graviton Kaluza-Klein modes give rise to a remarkable enhancement of such a deviation.

We discuss a constant contribution to meson correlators at finite temperature. In the deconfinement phase of QCD, a colored single quark state is allowed as a finite energy state, which yields to a contribution of wraparound quark propagation to temporal meson correlators. We investigate the effects in the free quark case and quenched QCD at finite temperature. The “scattering” contribution causes a constant mode in meson correlators with zero spatial momentum and degenerate quark masses, which can dominate the correlators in the region of large imaginary times. In the free spectral function, the contribution yields a term proportional to $\omega \delta (\omega )$. Therefore this contribution is related to transport phenomena in the quark gluon plasma. It is possible to distinguish the constant contribution from the other part using several analysis methods proposed in this paper. As a result of the analyses, we find that drastic changes in charmonium correlators for ${\chi }_c$ states just above the deconfinement transition are due to the constant contribution. The other differences in the ${\chi }_c$ states are small. It may indicate the survival of ${\chi }_c$ states after the deconfinement transition until, at least, $1.4T_c$.

We present a measurement of the inclusive production cross section for $Z$ bosons decaying to tau leptons in $p\overline{p}$ collisions at $\sqrt{s}=1.96\mathrm{TeV}$. We use a channel with one hadronically-decaying and one electronically-decaying tau. This measurement is based on $350{\mathrm{pb}}^{-1}$ of CDF Run II data. Using a sample of 504 opposite sign $e\tau$ events with a total expected background of 190 events, we obtain $\sigma (p\overline{p}\to 4Z)·\mathcal{B}(Z\to \tau \tau )=264\pm 23(\mathrm{stat})\pm 14(\mathrm{syst})\pm 15(\mathrm{lumi})\mathrm{pb}$, in agreement with the next-to-next-to-leading order QCD prediction. This is the first CDF cross section measurement using hadronically-decaying taus in Run II.

We study the Casimir piston for massless scalar fields obeying Dirichlet boundary conditions in a three-dimensional cavity with sides of arbitrary lengths $a$, $b$, and $c$ where $a$ is the plate separation. We obtain an exact expression for the Casimir force on the piston valid for any values of the three lengths. As in the electromagnetic case with perfect-conductor conditions, we find that the Casimir force is negative (attractive) regardless of the values of $a$, $b$, and $c$. Though cases exist where the interior contributes a positive (repulsive) Casimir force, the total Casimir force on the piston is negative when the exterior contribution is included. We also obtain an alternative expression for the Casimir force that is useful computationally when the plate separation $a$ is large.

The axion is one of the best motivated candidates for particle dark matter. We study and update the constraints imposed by the recent CMB and LSS experiments on the mass of axions produced by the misalignment mechanism, as a function of both the inflationary scale and the reheating temperature. Under some particular although not unconventional assumptions, the axion induces isocurvature perturbations with an amplitude too large to be compatible with observations. Specifically, for inflation taking place at intermediate energy scales, we derive some restrictive limits which can only be evaded by assuming an efficient reheating mechanism, with $T_{\mathrm{rh}}>{10}^{11}\mathrm{GeV}$. Chaotic inflation with a quadratic potential is still compatible with the axion scenario, provided that the Peccei-Quinn scale $f_a$ is close to ${10}^{10}$ or ${10}^{11}\mathrm{GeV}$. Isocurvature bounds eliminate the possibility of a larger $f_a$ and a small misalignment angle. We find that isocurvature constraints on the axion scenario must be taken into account whenever the scale of inflation is above ${10}^{12}\mathrm{GeV}$; below this scale, axionic isocurvature modes are too small to be probed by current observations.

We investigate the value of future dark-energy experiments by modeling their ability to constrain the dark-energy equation of state. Similar work was recently reported by the Dark Energy Task Force (DETF) using a two dimensional parameterization of the equation-of-state evolution. We examine constraints in a nine-dimensional dark-energy parameterization, and find that the best experiments constrain significantly more than two dimensions in our 9D space. Consequently the impact of these experiments is substantially beyond that revealed in the DETF analysis, and the estimated cost per “impact” drops by about a factor of 10 as one moves to the very best experiments. The DETF conclusions about the relative value of different techniques and of the importance of combining techniques are unchanged by our analysis.

We found 140 neutrino-induced muons in 854.24 live days in the MINOS far detector, which has an acceptance for neutrino-induced muons of $6.91\times {10}^6{\mathrm{cm}}^2\mathrm{sr}$. We looked for evidence of neutrino disappearance in this data set by computing the ratio of the number of low momentum muons to the sum of the number of high momentum and unknown momentum muons for both data and Monte Carlo expectation in the absence of neutrino oscillations. The ratio of data and Monte Carlo ratios, $\mathcal{R}$, is $\mathcal{R}={0.65}_{-0.12}^{+0.15}(\mathrm{stat})\pm 0.09(\mathrm{syst})$, a result that is consistent with an oscillation signal. A fit to the data for the oscillation parameters ${sin}^{2}2{\theta }_{23}$ and $\Delta m_{23}^2$ excludes the null oscillation hypothesis at the 94% confidence level. We separated the muons into ${\mu }^{-}$ and ${\mu }^{+}$ in both the data and Monte Carlo events and found the ratio of the total number of ${\mu }^{-}$ to ${\mu }^{+}$ in both samples. The ratio of those ratios, ${\widehat{\mathcal{R}}}_{CPT}$, is a test of $CPT$ conservation. The result ${\widehat{\mathcal{R}}}_{CPT}={0.72}_{-0.18}^{+0.24}(\mathrm{stat}{)}_{-0.04}^{+0.08}(\mathrm{syst})$ is consistent with $CPT$ conservation.

Assisted chaotic inflation in brane cosmology is discussed. We work in the framework of Randall-Sundrum (RS) II model, in which adopting the RS condition the only parameter is the five-dimensional Planck mass. Using the scalar spectral index and the amplitude of scalar perturbations we determine both the mass of the scalar fields responsible for inflation and the fundamental Planck mass of the higher-dimensional theory. We find that the mass of the scalars has the typical value of the inflaton mass in chaotic inflation ($M_I\sim {10}^{13}\mathrm{GeV}$) and that the five-dimensional Planck mass is very close to the grand unified theories (GUT) scale ($M_5\sim ({10}^{16}–{10}^{17})\mathrm{GeV}$). Furthermore, no matter how many scalar fields we use it is not possible to have chaotic inflation with field values below the fundamental Planck mass.

We introduce a method for extracting the cusp anomalous dimension at $L$ loops from four-gluon amplitudes in $\mathcal{N}=4$ Yang-Mills without evaluating any integrals that depend on the kinematical invariants. We show that the anomalous dimension only receives contributions from the obstructions introduced in [F. Cachazo, M. Spradlin, and A. Volovich, J. High Energy Phys. 07 (2006) 007]. We illustrate this method by extracting the two- and three-loop anomalous dimensions analytically and the four-loop one numerically. The four-loop result was recently guessed to be $f^{(4)}=-(4{\zeta }_2^3+24{\zeta }_2{\zeta }_4+50{\zeta }_6-4(1+r){\zeta }_3^2)$ with $r=-2$ using integrability and string theory arguments in [N. Beisert, B. Eden, and M. Staudacher, J. Stat. Mech. (2007) P021]. Simultaneously, $f^{(4)}$ was computed numerically in [Z. Bern, M. Czakon, L. J. Dixon, D. A. Kosower, and V. A. Smirnov, Phys. Rev. D 75, 085010 (2007)] from the four-loop amplitude obtaining, with best precision at the symmetric point $s=t$, $r=-2.028(36)$. Our computation is manifestly $s/t$ independent and improves the precision to $r=-2.00002(3)$, providing strong evidence in favor of the conjecture. The improvement is possible due to a large reduction in the number of contributing terms, as well as a reduction in the number of integration variables in each term.

Dynamics with noncommutative coordinates invariant under three-dimensional rotations or, if time is included, under Lorentz transformations is developed. These coordinates turn out to be the boost operators in $SO(1,3)$ or in $SO(2,3)$, respectively. The noncommutativity is governed by a mass parameter $M$. The principal results are: (i) a modification of the Heisenberg algebra for distances smaller than $1/M$, (ii) a lower limit, $1/M$, on the localizability of wave packets, (iii) discrete eigenvalues of the coordinate operator in timelike directions, and (iv) an upper limit, $M$, on the mass for which free field equations have solutions. Possible restrictions on small black holes are discussed.

There has been important experimental progress in the sector of heavy baryons in the past several years. We study the strong decays of the $S$-wave, $P$-wave, $D$-wave, and radially excited charmed baryons using the ${}^{3}P_0$ model. After comparing the calculated decay pattern and total width with the available data, we discuss the possible internal structure and quantum numbers of those charmed baryons observed recently.

This paper is devoted to the study of leading twist light cone wave functions of the $J/\Psi$ meson. The moments of these wave functions have been calculated within three approaches: potential models, nonrelativistic QCD, and QCD sum rules. Using the results obtained within these approaches the models for the light cone wave functions of leading twist have been proposed. Similarly to the wave function of the ${\eta }_c$ meson, the leading twist light cone wave functions of the $J/\Psi$ meson have very interesting properties at scales $\mu >m_c$: improvement of the accuracy of the model, appearance of a relativistic tail, and violation of nonrelativistic QCD velocity scaling rules. The last two properties are the properties of true leading twist light cone wave functions of the $J/\Psi$ meson.

We have extended the Polyakov-Nambu-Jona-Lasinio (PNJL) model for two degenerate flavors to include the isospin chemical potential (${\mu }_I$). All the diagonal and mixed derivatives of pressure with respect to the quark number (proportional to baryon number) chemical potential (${\mu }_0$) and isospin chemical potential up to sixth order have been extracted at ${\mu }_0={\mu }_I=0$. These derivatives give the generalized susceptibilities with respect to quark and isospin numbers. Similar estimates for the flavor diagonal and off-diagonal susceptibilities are also presented. Comparison to lattice QCD (LQCD) data of some of these susceptibilities for which LQCD data are available show similar temperature dependence, though there are some quantitative deviations above the crossover temperature. We have also looked at the effects of instanton induced flavor mixing coming from the $U_A(1)$ chiral symmetry breaking ’t Hooft determinantlike term in the NJL part of the model. The diagonal quark number and isospin susceptibilities are completely unaffected. The off-diagonal susceptibilities show significant dependence near the crossover. Finally we present the chemical potential dependence of specific heat and speed of sound within the limits of chemical potentials where neither diquarks nor pions can condense.

The absorption cross section of black holes has been investigated for various fields. Nevertheless, the absorption cross section of Schwarzschild black holes for the electromagnetic field has been only calculated in the low- and high-frequency approximations until now. Here we compute it numerically for arbitrary frequencies.

The singular field of a point charge has recently been described in terms of a new Green’s function of curved spacetime. This singular field plays an important role in the calculation of the self-force acting upon the particle. We provide a method for calculating the singular field and a catalog of expansions of the singular field associated with the geodesic motion of monopole and dipole sources for scalar, electromagnetic, and gravitational fields. These results can be used, for example, to calculate the effects of the self-force acting on a particle as it moves through spacetime.