Showing papers in "Progress of Theoretical and Experimental Physics in 2014"

Anomaly polynomial of general 6D SCFTs

Abstract: We describe a method to determine the anomaly polynomials of general 6d N=(2,0) and N=(1,0) SCFTs, in terms of the anomaly matching on their tensor branches. This method is almost purely field theoretical, and can be applied to all known 6d SCFTs. We demonstrate our method in many concrete examples, including N=(2,0) theories of arbitrary type and the theories on M5 branes on ALE singularities, reproducing the N 3 behavior. We check the results against the anomaly polynomials computed M-theoretically via the anomaly inflow.

Gravitational radiation from an axion cloud around a black hole: Superradiant phase

Abstract: Motivated by the possible existence of string axions with ultralight masses, we study gravitational radiation from an axion cloud around a rotating black hole (BH). The axion cloud extracts the rotation energy of the BH by superradiant instability, while it loses energy through the emission of gravitational waves (GWs). In this paper, GWs are treated as perturbations on a fixed background spacetime to derive the energy emission rate. We give an analytic approximate formula for the case where the axion Compton wavelength is much larger than the BH radius, and then present numerical results without approximation. The energy loss rate of the axion cloud through GW emission turns out to be smaller than the energy gain rate of the axion cloud by superradiant instability until nonlinear self-interactions of axions become important. In particular, an axion bosenova must happen at the last stage of superradiant instability.

Exact black hole solutions in shift symmetric scalar–tensor theories

Abstract: We derive a variety of exact black hole solutions in a subclass of Horndeski's scalar-tensor theory possessing shift symmetry, phi -> phi + c and reflection symmetry, phi -> -phi The theory admits two arbitrary functions of X := -(partial derivative phi)(2)/2, and our solutions are constructed without specifying the concrete form of the two functions, implying that black hole solutions in specific scalar-tensor theories found in the literature can be extended to a more general class of theories with shift symmetry. Our solutions include a black hole in the presence of an effective cosmological constant, the Nariai spacetime, the Lifshitz black hole, and other nontrivial solutions, all of which exhibit nonconstant scalar-field profiles.

Vortices and Other Topological Solitons in Dense Quark Matter

Abstract: Dense quantum chromodynamic matter accommodates various kind of topological solitons such as vortices, domain walls, monopoles, kinks, boojums, and so on. In this review, we discuss various properties of topological solitons in dense quantum chromodynamics (QCD) and their phenomenological implications. Particular emphasis is placed on the topological solitons in the color–flavor-locked (CFL) phase, which exhibits both superfluidity and superconductivity. The properties of topological solitons are discussed in terms of effective field theories such as the Ginzburg–Landau theory, the chiral Lagrangian, or the Bogoliubov–de Gennes equation. The most fundamental string-like topological excitations in the CFL phase are non-Abelian vortices, which are 1/3 quantized superfluid vortices and color magnetic flux tubes. These vortices are created at a phase transition by the Kibble–Zurek mechanism or when the CFL phase is realized in compact stars, which rotate rapidly. The interaction between vortices is found to be repulsive and consequently a vortex lattice is formed in rotating CFL matter. Bosonic and fermionic zero-energy modes are trapped in the core of a non-Abelian vortex and propagate along it as gapless excitations. The former consists of translational zero modes (a Kelvin mode) with a quadratic dispersion and CP2 Nambu–Goldstone gapless modes with a linear dispersion, associated with the CFL symmetry spontaneously broken in the core of a vortex, while the latter is Majorana fermion zero modes belonging to the triplet of the symmetry remaining in the core of a vortex. The low-energy effective theory of the bosonic zero modes is constructed as a non-relativistic free complex scalar field and a relativistic CP2 model in 1+1 dimensions. The effects of strange quark mass, electromagnetic interactions, and non-perturbative quantum corrections are taken into account in theCP2 effective theory.Various topological objects associated with non-Abelian vortices are studied; colorful boojums at the CFL interface, the quantum color magnetic monopole confined by vortices, which supports the notion of quark–hadron duality, and Yang–Mills instantons inside a non-Abelian vortex as lumps are discussed. The interactions between a non-Abelian vortex and quasiparticles such as phonons, gluons, mesons, and photons are studied. As a consequence of the interaction with photons, a vortex lattice behaves as a cosmic polarizer. As a remarkable consequence of Majorana fermion zero modes, non-Abelian vortices are shown to behave as a novel kind of non-Abelian anyon. In the order parameters of chiral symmetry breaking, we discuss fractional and integer axial domain walls, Abelian and non-Abelian axial vortices, axial wall–vortex composites, and Skyrmions.

Lattice energy–momentum tensor from the Yang–Mills gradient flow—inclusion of fermion fields

Abstract: Local products of fields deformed by the so-called Yang--Mills gradient flow become renormalized composite operators. This fact has been utilized to construct a correctly normalized conserved energy--momentum tensor in the lattice formulation of the pure Yang--Mills theory. In the present paper, this construction is further generalized for vector-like gauge theories containing fermions.

Entanglement of local operators in large-N conformal field theories

Abstract: In this paper, we study Renyi and von Neumann entanglement entropy of excited states created by local operators in large-$N$ (or large-central-charge) conformal field theories (CFTs). First we point out that a naive large-$N$ expansion can break down for the von Neumann entanglement entropy, while it does not for the Renyi entanglement entropy. This happens even for the excited states in free Yang–Mills theories. Next, we analyze strongly coupled large-$N$ CFTs from both the field-theoretic and holographic viewpoints. We find that the Renyi entanglement entropy of the excited state, produced by a local operator, grows logarithmically under its time evolution and its coefficient is proportional to the conformal dimension of the local operator.

IceCube PeV-EeV neutrinos and secret interactions of neutrinos

Abstract: We show that the PeV neutrinos detected by IceCube put unique constraints on "secret" interactions of neutrinos with the cosmic neutrino background (C$ u$B). The coupling must be $g <0.03$ for the mediating boson mass $m_{X} \lesssim 2$ MeV, $g/m_{X} < 5$ GeV$^{-1}$ for $m_{X} \gtrsim 20$ MeV, and $g/m_{X} < 0.07$ GeV$^{-1}$ in between. We also investigate the possibility that neutrino cascades degrade high-energy neutrinos to PeV energies by upgrading C$ u$B where the energy flux of PeV neutrinos can coincide with the Waxman-Bahcall bound or the cosmogenic neutrino flux for protons, thanks to energy conservation. However a large coupling is required, which is disfavored by laboratory decay constraints. The suppression of PeV-EeV neutrinos is a testable prediction for the Askaryan Radio Array.

Higgs branch localization of 3d = 2 theories

Abstract: We study $\mathcal {N}=2$ supersymmetric gauge theories on a squashed 3-sphere and $\mathbb {S}^1 \times \mathbb {S}^2$. Recent studies have shown that the partition functions in a class of $\mathcal {N}=2$ theories have factorized forms in terms of vortex and anti-vortex partition functions by explicitly evaluating matrix integrals obtained from Coulomb branch localization. We directly derive this structure by performing Higgs branch localization. It turns out that more general $\mathcal {N}=2$ theories have this factorization property. We also discuss the factorization of the supersymmetric Wilson loop.

Possible existence of viable models of bi-gravity with detectable graviton oscillations by gravitational wave detectors

Abstract: Possible existence of viable models of bi-gravity with detectable graviton oscillations by gravitational wave detectors Antonio De Felice1,2,3,∗, Takashi Nakamura4,∗, and Takahiro Tanaka3,∗ 1ThEP’s CRL, NEP, The Institute for Fundamental Study, Naresuan University, Phitsanulok 65000, Thailand 2Thailand Center of Excellence in Physics, Ministry of Education, Bangkok 10400, Thailand 3Yukawa Institute for Theoretical Physics, Kyoto 606-8502, Japan 4Department of Physics, Kyoto University, Kyoto 606-8502, Japan ∗E-mail: antonio.defelice@yukawa.kyoto-u.ac.jp, takashi@tap.scphys.kyoto-u.ac.jp, tanaka@yukawa.kyoto-u.ac.jp

Observation of tau neutrino appearance in the CNGS beam with the OPERA experiment

Abstract: The OPERA experiment is searching for nu_mu -> nu_tau oscillations in appearance mode i.e. via the direct detection of tau leptons in nu_tau charged current interactions. The evidence of nu_mu -> nu_tau appearance has been previously reported with three nu_tau candidate events using a sub-sample of data from the 2008-2012 runs. We report here a fourth nu_tau candidate event, with the tau decaying into a hadron, found after adding the 2012 run events without any muon in the final state to the data sample. Given the number of analysed events and the low background, nu_mu -> nu_tau oscillations are established with a significance of 4.2sigma.

Minimal Higgs inflation

Abstract: We consider a possibility that the Higgs field in the Standard Model (SM) serves as an inflaton when its value is around the Planck scale. We assume that the SM is valid up to an ultraviolet cutoff scale \Lambda, which is slightly below the Planck scale, and that the Higgs potential becomes almost flat above \Lambda. Contrary to the ordinary Higgs inflation scenario, we do not assume the huge non-minimal coupling, of O(10^4), of the Higgs field to the Ricci scalar. We find that \Lambda must be less than 5*10^{17}GeV in order to explain the observed fluctuation of the cosmic microwave background, no matter how we extrapolate the Higgs potential above \Lambda. The scale 10^{17}GeV coincides with the perturbative string scale, which suggests that the SM is directly connected with the string theory. For this to be true, the top quark mass is restricted to around 171GeV, with which \Lambda can exceed 10^{17}GeV. As a concrete example of the potential above \Lambda, we propose a simple log type potential. The predictions of this specific model for the e-foldings N_*=50--60 are consistent with the current observation, namely, the scalar spectral index is n_s=0.977--0.983 and the tensor to scalar ratio 0

The integrated Sachs–Wolfe effect and the Rees–Sciama effect

Abstract: It has been around fifty years since R. K. Sachs and A. M. Wolfe predicted the existence of anisotropy in the Cosmic Microwave Background (CMB) and ten years since the integrated Sachs Wolfe effect (ISW) was first detected observationally. The ISW effect provides us with a unique probe of the accelerating expansion of the Universe. The cross-correlation between the large-scale structure and CMB has been the most promising way to extract the ISW effect from the data. In this article, we review the physics of the ISW effect and summarize recent observational results and interpretations.

Results from the Wilkinson Microwave Anisotropy Probe

Abstract: The Wilkinson Microwave Anisotropy Probe (WMAP) mapped the distribution of temperature and polarization over the entire sky in five microwave frequency bands. These full-sky maps were used to obtain measurements of temperature and polarization anisotropy of the cosmic microwave background with the unprecedented accuracy and precision. The analysis of two-point correlation functions of temperature and polarization data gives determinations of the fundamental cosmological parameters such as the age and composition of the universe, as well as the key parameters describing the physics of inflation, which is further constrained by three-point correlation functions. WMAP observations alone reduced the flat Λ cold dark matter (Lambda Cold Dark Matter) cosmological model (six) parameter volume by a factor of > 68, 000 compared with pre-WMAP measurements. The WMAP observations (sometimes in combination with other astrophysical probes) convincingly show the existence of non-baryonic dark matter, the cosmic neutrino background, flatness of spatial geometry of the universe, a deviation from a scale-invariant spectrum of initial scalar fluctuations, and that the current universe is undergoing an accelerated expansion. The WMAP observations provide the strongest ever support for inflation; namely, the structures we see in the universe originate from quantum fluctuations generated during inflation.

Strong restriction on inflationary vacua from the local gauge invariance III: Infrared regularity of graviton loops

Abstract: It has been claimed that the super-Hubble modes of the graviton generated during inflation can make loop corrections diverge. Even if we introduce an infrared (IR) cutoff at a comoving scale as an ad hoc but practical method of regularization, we encounter secular growth, which may lead to the breakdown of perturbative expansion for a sufficiently long-lasting inflation. In this paper, we show that the IR pathology concerning the graviton can be attributed to the presence of residualgauge degrees of freedom in the local observable universe, as in the case of the adiabatic curvature perturbation. We will show that choosing the Euclidean vacuum as the initial state ensuresinvarianceundertheabove-mentionedresidualgaugetransformations.Wewillalsoshow that, as long as we consider a gauge invariant quantity in the local universe, we encounter neither IR divergence nor secular growth. The argument in this paper applies to general single-field models of inflation up to a sufficiently high order in perturbation.

Heat transport as torsional responses and Keldysh formalism in a curved spacetime

Abstract: Heat transport phenomena are of scientific and technological importance. Especially the thermal Hall effect is an interesting phenomenon in which the heat current flows perpendicular to a temperature gradient. Recent experiments revealed the effects of inelastic scattering on the anomalous Hall effect in ferromagnetic metals [1] and detected the magnon Hall effect in a ferromagnetic insulator [2]. A systematic framework for calculating the thermal Hall conductivity (THC) is highly desired. Theoretically, the Kubo formula for the thermal conductivity is well established by introducing a gravitational potential [3], while that for the THC alone is not sufficient and should be augmented with the heat magnetization (HM) [4, 5]. Previous theories are unsatisfactory; it remains unclear how the scaling assumptions on the charge and heat currents are justified and furthermore how the theories are practically applied to disordered or interacting systems. In this talk, we revisit the basics of heat transport from the gauge-theoretical viewpoint [6]. We begin with the Noether theorem and gauge principle and explain why a theory of heat transport involves gravity. A vielbein is a gauge field of gravity which is coupled to the energy current and induces a field strength called torsion. A torsional electric field is equivalent to a temperature gradient, and a torsional magnetic field is conjugate to the HM. Such a gauge-theoretical discussion yields the natural definition of the HM. We also develop the Keldysh formalism in a curved spacetime to calculate these gravitational responses [6]. This is a natural extension of the gaugecovariant Keldysh formalism [7] by taking into account gauge fields of gravity. We derive the Green-function formulas for the Kubo-formula contribution and the HM applicable to disordered or interacting systems. In the clean and noninteracting limit, we reproduce the Berry-phase formula for the THC which satisfies the Wiedemann-Franz law [5].

Enhancement of muonium emission rate from silica aerogel with a laser-ablated surface

Abstract: e ) atoms from a laser-processed aerogel surface into vacuumwas studied for the rst time. Laser ablation was used to create hole-like regions withdiameter of about 270 m in a triangular pattern with hole separation in the range of300{500 m. The emission probability for the laser-processed aerogel sample is at leasteight times higher than for a uniform one.

The Ramond sector of heterotic string field theory

Abstract: We attempt to construct the full equations of motion for the Neveu-Schwarz and the Ramond sectors of the heterotic string field theory. Although they are non-polynomial also in the Ramond string field $\Psi$, we can construct them order by order in $\Psi$. Their explicit forms with the gauge transformations are given up to the next-to-next-to-leading order in $\Psi$. We also determine a subset of the terms to all orders. By introducing an auxiliary Ramond string field $\Xi$, we construct a covariant action supplemented with a constraint, which should be imposed on the equations of motion. We propose the Feynman rules and show how they reproduce well-known physical four-point amplitudes with external fermions.

Stability of the Schwarzschild–de Sitter black hole in the dRGT massive gravity theory

Abstract: The Schwarzschild–de Sitter solution in the Einstein theory with a positive cosmological constant $\Lambda =m^2/\alpha $ becomes an exact solution to the de Rham–Gabadadze–Tolley (dRGT) nonlinear massive gravity theory with the mass parameter $m$ when the theory parameters $\alpha $ and $\beta $ satisfy the relation $\beta =\alpha ^2$. We study the perturbative behavior of this black hole solution in the nonlinear dRGT theory with $\beta =\alpha ^2$. We find that the linear perturbation equations become identical to those for the vacuum Einstein theory when they are expressed in terms of gauge-invariant variables. This implies that this black hole is stable in the dRGT theory as far as the spacetime structure is concerned, in contrast to the case of the bi-Schwarzschild solution in the bi-metric theory. However, we have also found a pathological feature that the general solution to the perturbation equations contain a single arbitrary function of spacetime coordinates. This implies a degeneracy of dynamics in the Stuckelberg field sector at the linear perturbation level in this background. The physical significance of this degeneracy depends on how the Stuckelberg fields couple observable fields.

Axion monodromy inflation with sinusoidal corrections

Abstract: We study the axion monodromy inflation with a non-perturbatively generated sinusoidal term. The potential form is a mixture between the natural inflation and the axion monodromy inflation potentials. The sinusoidal term is subdominant in the potential, but leaves significant effects on the resultant fluctuation generated during inflation. A larger tensor-to-scalar ratio can be obtained in our model. We study two scenarios, single inflation scenario and the double inflation scenario. In the first scenario, the axion monodromy inflation with a sufficient number of e-fold generates a larger tensor-to-scalar ratio about $0.1 - 0.15$ but also a tiny running of spectral index. In the second scenario of double inflation, axion monodromy inflation is its first stage and, we assume another inflation follows. In this case, our model can realize a larger tensor-to-scalar ratio and a large negative running of spectral index simultaneously.

Fundamental phenomena of quantum mechanics explored with neutron interferometers

Abstract: Ongoing fascination with quantum mechanics keeps driving the development of the wide field of quantum-optics, including its neutron-optics branch. Application of neutron-optical methods and, especially, neutron interferometry and polarimetry has a long-standing tradition for experimental investigations of fundamental quantum phenomena. We give an overview of related experimental efforts made in recent years.

Covariant approach to the no-ghost theorem in massive gravity

Abstract: We discuss the no-ghost theorem in the massive gravity in a covariant manner. Using the BRST formalism and St\"{u}ckelberg fields, we first clarify how the Boulware-Deser ghost decouples in the massive gravity theory with Fierz-Pauli mass term. Here we find that the crucial point in the proof is that there is no higher (time) derivative for the St\"{u}ckelberg `scalar' field. We then analyze the nonlinear massive gravity proposed by de Rham, Gabadadze and Tolley, and show that there is no ghost for general admissible backgrounds. In this process, we find a very nontrivial decoupling limit for general backgrounds. We end the paper by demonstrating the general results explicitly in a nontrivial example where there apparently appear higher time derivatives for St\"{u}ckelberg scalar field, but show that this does not introduce the ghost into the theory.

Quantum near-horizon geometry of a black 0-brane

Abstract: We investigate a bunch of D0-branes to reveal its quantum nature from the gravity side. In the classical limit, it is well described by a non-extremal black 0-brane in type IIA supergravity. The solution is uplifted to the eleven dimensions and expressed by a non-extremal M-wave solution. After reviewing the effective action for the M-theory, we explicitly solve the equations of motion for the near horizon geometry of the M-wave. As a result we derive an unique solution which includes the effect of the quantum gravity. Thermodynamic property of the quantum near horizon geometry of the black 0-brane is also studied by using Wald's formula. Combining our result with that of the Monte Carlo simulation of the dual thermal gauge theory, we find strong evidence for the gauge/gravity duality in the D0-branes system at the level of quantum gravity.

Mass and radius formulas for low-mass neutron stars

Abstract: Neutron stars, produced at the death of massive stars, are often regarded as giant neutron-rich nuclei. This picture is especially relevant for low-mass (below about solar mass, $M_\odot $) neutron stars, where non-nucleonic components are not expected to occur. Due to the saturation property of nucleonic matter, leading to the celebrated liquid-drop picture of atomic nuclei, empirical nuclear masses and radii can be approximately expressed as a function of atomic mass number. It is, however, not straightforward to express masses and radii of neutron stars even in the low-mass range where the structure is determined by a balance between the pressure of neutron-rich nucleonic matter and gravity. Such expressions would be of great use given possible simultaneous mass and radius measurements. Here we successfully construct theoretical formulas for the masses and radii of low-mass neutron stars from various models that are consistent with empirical masses and radii of stable nuclei. In this process, we discover a new equation-of-state parameter that characterizes the structure of low-mass neutron stars. This parameter, which plays a key role in connecting the mass–radius relation of the laboratory nuclei to that of the celestial objects, could be constrained from future observations of low-mass neutron stars.

Self-organization in foliated phase space: Construction of a scale hierarchy by adiabatic invariants of magnetized particles

Abstract: Adiabatic invariants foliate phase space, and impart a macro-scale hierarchy by separating microscopic variables. On a macroscopic leaf, long-scale ordered structures are created while maximizing entropy. A plasma confined in a magnetosphere is invoked for unveiling the organizing principle ---in the vicinity of a magnetic dipole, the plasma self-organizes to a state with a steep density gradient. The resulting nontrivial structure has maximum entropy in an appropriate, constrained phase space. One could view such a phase space as a leaf foliated in terms of Casimir invariants ---adiabatic invariants measuring the number of quasi-particles (macroscopic representation of periodic motions) are identified as the relevant Casimir invariants. The density clump is created in response to the inhomogeneity of the energy level (frequency) of quasi-particles.

An extended standard model and its Higgs geometry from the matrix model

Abstract: We nd a simple brane conguration in the IKKT matrix model which resembles the standard model at low energies, with a second Higgs doublet and right-handed neutrinos. The electroweak sector is realized geometrically in terms of two minimal fuzzy ellipsoids, which can be interpreted in terms of four D0 branes in the extra dimensions. The electroweak Higgs connects the D0 branes and is an indispensable part of the geometry. Fermionic would-be zero modes arise at the intersections with two larger branes, leading precisely to the correct chiral matter

Observation of coherent two-photon emission from the first vibrationally excited state of hydrogen molecules

Abstract: Yuki Miyamoto1, Hideaki Hara1, Susumu Kuma1,†, Takahiko Masuda1, Itsuo Nakano1, Chiaki Ohae2,‡, Noboru Sasao1,∗, Minoru Tanaka3, Satoshi Uetake4,∗, Akihiro Yoshimi1, Koji Yoshimura1, and Motohiko Yoshimura4 1Research Core for Extreme Quantum World, Okayama University, Okayama 700-8530, Japan 2Graduate School of Natural Science and Technology, Okayama University, Okayama 700-8530, Japan 3Department of Physics, Osaka University, Toyonaka, Osaka 560-0043, Japan 4Research Center of Quantum Universe, Okayama University, Okayama 700-8530, Japan ∗E-mail: sasao@okayama-u.ac.jp, uetake@okayama-u.ac.jp

Generalized spin-wave theory: Application to the bilinear–biquadratic model

Abstract: Rodrigo A. Muniz1,2, Yasuyuki Kato3,4, and Cristian D. Batista3† 1Department of Physics and Institute for Optical Sciences, University of Toronto, Toronto ON, M5S 1A7, Canada 2International Institute of Physics UFRN, Natal, RN 59078-400, Brazil 3Theoretical Division, T-4 and CNLS, Los Alamos National Laboratory, Los Alamos, NM 87545, USA 4RIKEN Center for Emergent Matter Science (CEMS), Wako-shi, Saitama 351-0198, Japan ∗E-mail: yasuyuki.kato@riken.jp

φ photoproduction with coupled-channel effects

Abstract: We study φ photoproduction with various hadronic rescattering contributions included, in addition to the Pomeron and pseudoscalar meson-exchange diagrams. We find that the hadronic rescattering diagrams can explain the recent experimental data in the vicinity of the threshold. In particular, the bump-like structure at the photon energy Eγ ≈ 2.3 GeV is well explained by the K(1520) rescattering amplitude in the intermediate state, which is the dominant contribution among other hadronic contributions. We also find that the hadronic rescattering diagrams are consistent with the observed spin-density matrix elements near the threshold region.