Large Symmetry Research Articles

Heavy nuclei as thermal insulation for protoneutron stars

A proto-neutron star (PNS) is a newly formed compact object in a core collapse supernova. In this Letter, the neutrino emission from the cooling process of a PNS is investigated using two types of nuclear equation of state (EOS). It is found that the neutrino signal is mainly determined by the high-density EOS. The neutrino luminosity and mean energy are higher and the cooling time scale is longer for the softer EOS. Meanwhile, the neutrino mean energy and the cooling time scale are also affected by the low-density EOS because of the difference in the population of heavy nuclei. Heavy nuclei have a large scattering cross section with neutrinos owing to the coherent effects and act as thermal insulation near the surface of a PNS. The neutrino mean energy is higher and the cooling time scale is longer for an EOS with a large symmetry energy at low densities, namely a small density derivative coefficient of the symmetry energy, $L$.

Modal Noise Mitigation through Fiber Agitation for Fiber-fed Radial Velocity Spectrographs

Abstract Optical fiber modal noise is a limiting factor for high precision spectroscopy signal-to-noise in the near-infrared and visible. Unabated, especially when using highly coherent light sources for wavelength calibration, modal noise can induce radial velocity (RV) errors that hinder the discovery of low-mass (and potentially Earth-like) planets. Previous research in this field has found sufficient modal noise mitigation through the use of an integrating sphere, but this requires extremely bright light sources, a luxury not necessarily afforded by the next generation of high-resolution optical spectrographs. Otherwise, mechanical agitation, which “mixes” the fiber’s modal patterns and allows the noise to be averaged over minutes-long exposures, provides some noise reduction but the exact mechanism behind improvement in signal-to-noise and RV drift has not been fully explored or optimized by the community. Therefore, we have filled out the parameter space of modal noise agitation techniques in order to better understand agitation’s contribution to mitigating modal noise and to discover a better method for agitating fibers. We find that modal noise is best suppressed by the quasi-chaotic motion of two high-amplitude agitators oscillating with varying phase for fibers with large core diameters and low azimuthal symmetry. This work has subsequently influenced the design of a fiber agitator, to be installed with the EXtreme PREcision Spectrograph, that we estimate will reduce modal-noise-induced RV error to less than 3.2 cm s−1.

Asymptotic dynamics in perturbative quantum gravity and BMS supertranslations

Recently it has been shown that infrared divergences in the conventional S-matrix elements of gauge and gravitational theories arise from a violation of the conservation laws associated with large gauge symmetries. These infrared divergences can be cured by using the Faddeev-Kulish (FK) asymptotic states as the basis for S-matrix elements. Motivated by this connection, we study the action of BMS supertranslations on the FK asymptotic states of perturbative quantum gravity. We compute the BMS charge of the FK states and show that it characterizes the superselection sector to which the state belongs. Conservation of the BMS charge then implies that there is no transition between different superselection sectors, hence showing that the FK graviton clouds implement the necessary transition induced by the scattering process.

Recent development in theoretical studies of hyperon-nucleon interaction

Hypernuclear physics is the study of hypernuclei, their decays and productions, and the role they play in other related fields. It has always been at the frontier of experimental and theoretical nuclear physics since the quantum number strangeness was introduced and the first Λ hypernuclus was discovered in 1953. In recent years, open questions such as the large change symmetry breaking in A =4 Λ hypernuclei, the overbinding problem of A =5 Λ hypernucleus, the existence of the H-dibaryon and the hyperon puzzle in neutron stars have attracted a lot of attention. Today facilities like J-PARC, KEK, JLab, MAMI and COSY allow one to study the properties of hypernuclei with a precision and scope hitherto impossible. The experiments focus not only on the spectroscopy and weak decays of hypernuclei with strangeness S= − 1 and S = − 2, but also on the fundamental ΣN cross sections. In the meantime, theoretical techniques of few- and many-body calculations for hypernuclei have made steady progress, such as the Gaussian expansion method, the lattice QCD simulations and the Dirac-Brueckner-Hartree-Fock approach. Hyperon-nucleon interaction is the key input of the hypernuclear few- and many-body calculations. It plays a fundamental role in the microscopic understanding of hypernuclear physics. Meanwhile, it can also help improve our understanding of the role of strangeness in particle and nuclear physics, as well as the SU(3) symmetry and its breaking. In this paper, we first review the origin of hypernuclear physics and enmumerrate the aforementioned open questions of current interest. These outstanding issues reflect that the hyerpon-nucleon interaction is not fully understood so far. Then we discuss at length the history and current status of theoratical studies of hyperon-nucleon interaction, which are mainly performed in phenomenological models, lattice quantumchromo dynamics (lattice QCD) simulations and chiral effective field theory. The construction of phenomenological models, such as meson exchange models and quark models, has a rather long history. However, they predict very different results even for some of the low-energy phase shifts and scattering lengths, owing to the rather loose constraint from the small number of hyperon-nucleon scattering data. Lattice QCD simulations have made impressive progress since the 21st century, which provide an ab-initio numerical solution to QCD from first principles. With the ever-growing computing power and evolving numerical algorithms, lattice QCD simulations are getting close to the physical point (but still with large error bars). As the effective theory of low-energy QCD, chiral effective field theory has proven to be a useful tool in studies of low-energy strong interaction phenomena. The main feature of this approach is that by using a proper power counting scheme, one can improve calculations systematically by going to higher orders in powers of external momenta and light quark masses, and meantime the uncertainties of any given order. Furthermore, three- and four-body forces can be derived in a consistent manner. Studies of hadron-hadron interaction in chiral effective field theory have made remarkable progress in the past two decades and in the last part of this article we discuss the recent construction of hyperon-nucleon interaction in chiral effective field theory in detail.

Asymptotic U(1) charges at spatial infinity

Large gauge symmetries in Minkowski spacetime are often studied in two distinct regimes: either at asymptotic (past or future) times or at spatial infinity. By working in harmonic gauge, we provide a unified description of large gauge symmetries (and their associated charges) that applies to both regimes. At spatial infinity the charges are conserved and interpolate between those defined at the asymptotic past and future. This explains the equality of asymptotic past and future charges, as recently proposed in connection with Weinberg’s soft photon theorem.

D-brane SM-like and scalar dark matter in type IIA superstring theory

In light of the present LHC Run II at $\sqrt{s}=13$ $TeV$, string y standard-like model is studied. Concretely, a singlet $S $ scalar-extended SM given in terms four stacks of intersecting D6-branes in a type IIA superstring compactification producing a large gauge symmetry is examined. The involved scales are dealt with. According to the dark matter relic density, the mass of the scalar dark matter beyond the SM $m_{S}\lesssim 10^{3}GeV$ and the corresponding Higgs portal couplings $\lambda _{SH}\lesssim 10^{-8}$ are approached.

Soft hair as a soft wig

We consider large gauge transformations of gravity and electromagnetism in asymptotically flat spacetime. Already at the classical level, we identify a canonical transformation that decouples the soft variables from the hard dynamics. We find that only the soft dynamics is constrained by BMS or large charge conservation. Physically this corresponds to the fact that sufficiently long-wavelength photons or gravitons that are added to the in-state will simply pass through the interaction region; they scatter trivially in their own sector. This implies in particular that the large gauge symmetries bear no relevance to the black hole information paradox. We also present the quantum version of soft decoupling. As a consistency check, we show that the apparent mixing of soft and hard modes in the original variables arises entirely from the long range field of the hard charges, which is fixed by gauge invariance and so contains no additional information.

New insights into Mesozoic cycad evolution: an exploration of anatomically preserved Cycadaceae seeds from the Jurassic Oxford Clay biota

Most knowledge concerning Mesozoic Era floras has come from compression fossils. This has been augmented in the last 20 years by rarer permineralized material showing cellular preservation. Here, we describe a new genus of anatomically preserved gymnosperm seed from the Callovian–Oxfordian (Jurassic) Oxford Clay Formation (UK), using a combination of traditional sectioning and synchrotron radiation X-ray micro-tomography (SRXMT). Oxfordiana motturii gen. et sp. nov. is large and bilaterally symmetrical. It has prominent external ribs, and has a three-layered integument comprising: a narrow outer layer of thick walled cells; a thick middle parenchymatous layer; and innermost a thin fleshy layer. The integument has a longitudinal interior groove and micropyle, enveloping a nucellus with a small pollen chamber. The large size, bilateral symmetry and integumentary groove demonstrate an affinity for the new species within the cycads. Moreover, the internal groove in extant taxa is an autapomorphy of the genus Cycas, where it facilitates seed germination. Based upon the unique seed germination mechanism shared with living species of the Cycadaceae, we conclude that O. motturii is a member of the stem-group lineage leading to Cycas after the Jurassic divergence of the Cycadaceae from other extant cycads. SRXMT—for the first time successfully applied to fossils already prepared as slides—reveals the distribution of different mineral phases within the fossil, and allows us to evaluate the taphonomy of Oxfordiana. An early pyrite phase replicates the external surfaces of individual cells, a later carbonate component infilling void spaces. The resulting taphonomic model suggests that the relatively small size of the fossils was key to their exceptional preservation, concentrating sulfate-reducing bacteria in a locally closed microenvironment and thus facilitating soft-tissue permineralization.

Heavy quarkonium hybrids: Spectrum, decay, and mixing

We present a largely model independent analysis of the lighter Heavy Quarkonium Hybrids based on the strong coupling regime of Potential Non-Relativistic QCD (pNRQCD). We calculate the spectrum at leading order, including the mixing of static hybrid states. We use potentials that fulfill the required short and long distance theoretical constraints and fit well the available lattice data. We argue that the decay width to the lower lying Heavy Quarkonia can be reliably estimated in some cases, and provide results for a selected set of decays. We also consider the mixing with Heavy Quarkonium states. We establish the form of the mixing potential at $O(1/m_Q)$, $m_Q$ being the mass of the heavy quarks, and work out its short and long distance constraints. The weak coupling regime of pNRQCD and the effective string theory of QCD are used for that goal. We show that the mixing effects may indeed be important and produce large spin symmetry violations. Most of the isospin zero XYZ states fit well in our spectrum, either as a Hybrid or standard Quarkonium candidates.

Oxide Epitaxy with Large Symmetry Mismatch: Bronze-phase VO2 on SrTiO3

Oxide Epitaxy with Large Symmetry Mismatch: Bronze-phase VO₂ on SrTiO₃

Non-degenerate para-complex structures in 6D with large symmetry groups

For an almost product structure J on a manifold M of dimension 6 with non-degenerate Nijenhuis tensor $$N_J$$ , we show that the automorphism group $$G=\mathrm{Aut}(M,J)$$ has dimension at most 14. In the case of equality G is the exceptional Lie group $$G_2^*$$ . The next possible symmetry dimension is proved to be equal to 10, and G has Lie algebra $$\mathfrak {sp}(4,{\mathbb R})$$ . Both maximal and submaximal symmetric structures are globally homogeneous and strictly nearly para-Kahler. We also demonstrate that whenever the symmetry dimension is at least 9, then the automorphism algebra acts locally transitively.

Gauge fields with respect to d=(3+1) in the Kaluza\u2013Klein theories and in the spin-charge-family theory

It is shown that in the spin-charge-family theory (Mankoč Borštnik in arXiv:1607.01618v2, 2016, Phys Rev D 91:065004. arxiv:1409.7791, 2015, J Mod Phys 6:2244. doi:10.4236/jmp.2015.615230. arXiv: 1409.4981, 2015, J Mod Phys 4:823. doi:10.4236/jmp.2013.46113. arxiv:1312.1542, 2013, arxiv:1409.4981, 2014) as well as in all the Kaluza–Klein like theories (Blagojević in Gravitation and gauge symmetries, IoP Publishing, Bristol, 2002, An introduction to Kaluza–Klein theories, World Scientific, Singapore, 1983), vielbeins and spin connections manifest in d=(3+1) space equivalent vector gauge fields, when space with dge 5 has a large enough symmetry. The authors demonstrate this equivalence in spaces with the symmetry of the metric tensor in the space out of d=(3+1)-g^{sigma tau } = eta ^{sigma tau } f^{2} – for any scalar function f of the coordinates x^{sigma }, where x^{sigma } denotes the coordinates of space out of d=(3+1). Also the connection between vielbeins and scalar gauge fields in d=(3+1) (offering the explanation for the Higgs scalar) is discussed.

Kant, Schlick and Friedman on Space, Time and Gravity in Light of Three Lessons from Particle Physics

Kantian philosophy of space, time and gravity is significantly affected in three ways by particle physics. First, particle physics deflects Schlick’s General Relativity-based critique of synthetic a priori knowledge. Schlick argued that since geometry was not synthetic a priori, nothing was—a key step toward logical empiricism. Particle physics suggests a Kant-friendlier theory of space-time and gravity presumably approximating General Relativity arbitrarily well, massive spin-2 gravity, while retaining a flat space-time geometry that is indirectly observable at large distances. The theory’s roots include Seeliger and Neumann in the 1890s and Einstein in 1917 as well as 1920s–1930s physics. Such theories have seen renewed scientific attention since 2000 and especially since 2010 due to breakthroughs addressing early 1970s technical difficulties. Second, particle physics casts additional doubt on Friedman’s constitutive a priori role for the principle of equivalence. Massive spin-2 gravity presumably should have nearly the same empirical content as General Relativity while differing radically on foundational issues. Empirical content even in General Relativity resides in partial differential equations, not in an additional principle identifying gravity and inertia. Third, Kant’s apparent claim that Newton’s results could be known a priori is undermined by an alternate gravitational equation. The modified theory has a smaller (Galilean) symmetry group than does Newton’s. What Kant wanted from Newton’s gravity is impossible due its large symmetry group, but is closer to achievable given the alternative theory.

Erratum to: Almost complex structures in 6D with non-degenerate Nijenhuis tensors and large symmetry groups

We correct an error in the second part of Theorem 3 of our original paper.

Identical Wells, Symmetry Breaking, and the Near-Unitary Limit

Energy level splitting from the unitary limit of contact interactions to the near unitary limit for a few identical atoms in an effectively one-dimensional well can be understood as an example of symmetry breaking. At the unitary limit in addition to particle permutation symmetry there is a larger symmetry corresponding to exchanging the $N!$ possible orderings of $N$ particles. In the near unitary limit, this larger symmetry is broken, and different shapes of traps break the symmetry to different degrees. This brief note exploits these symmetries to present a useful, geometric analogy with graph theory and build an algebraic framework for calculating energy splitting in the near unitary limit.

The hidden symmetry of the heterotic string

We propose that Borcherds' Fake Monster Lie algebra is a broken symmetry of heterotic string theory compactified on $T^7 \times T^2$. As evidence, we study the fully flavored counting function for BPS instantons contributing to a certain loop amplitude. The result is controlled by $\Phi_{12}$, an automorphic form for $O(2, 26, \mathbb{Z})$. The degeneracies it encodes in its Fourier coefficients are graded dimensions of a second-quantized Fock space for this large symmetry algebra. This construction provides a concrete realization of Harvey and Moore's proposed relationship between Generalized Kac-Moody symmetries and supersymmetric string vacua.

Nanoscale self-templating for oxide epitaxy with large symmetry mismatch

Direct observations using scanning transmission electron microscopy unveil an intriguing interfacial bi-layer that enables epitaxial growth of a strain-free, monoclinic, bronze-phase VO2(B) thin film on a perovskite SrTiO3 (STO) substrate. We observe an ultrathin (2–3 unit cells) interlayer best described as highly strained VO2(B) nanodomains combined with an extra (Ti,V)O2 layer on the TiO2 terminated STO (001) surface. By forming a fully coherent interface with the STO substrate and a semi-coherent interface with the strain-free epitaxial VO2(B) film above, the interfacial bi-layer enables the epitaxial connection of the two materials despite their large symmetry and lattice mismatch.

Large gauge symmetries and asymptotic states in QED

Large Gauge Transformations (LGT) are gauge transformations that do not vanish at infinity. Instead, they asymptotically approach arbitrary functions on the conformal sphere at infinity. Recently, it was argued that the LGT should be treated as an infinite set of global symmetries which are spontaneously broken by the vacuum. It was established that in QED, the Ward identities of their induced symmetries are equivalent to the Soft Photon Theorem. In this paper we study the implications of LGT on the S-matrix between physical asymptotic states in massive QED. In appose to the naively free scattering states, physical asymptotic states incorporate the long range electric field between asymptotic charged particles and were already constructed in 1970 by Kulish and Faddeev. We find that the LGT charge is independent of the particles' momenta and may be associated to the vacuum. The soft theorem's manifestation as a Ward identity turns out to be an outcome of not working with the physical asymptotic states.

Structure of theAl13Co4(100) surface: Combination of surface x-ray diffraction andab initiocalculations

The structure of the quasicrystalline approximant ${\mathrm{Al}}_{13}{\mathrm{Co}}_{4}$(100) has been determined by surface x-ray diffraction (SXRD) and complementary density-functional-theory (DFT) calculations. Thanks to the use of a two-dimensional pixel detector, which speeds up the data acquisition enormously, an exceptionally large set of experimental data, consisting of 124 crystal truncation rods, has been collected and used to refine this complex structure of large unit cell and low symmetry. Various models were considered for the SXRD analysis. The best fit is consistent with a surface termination at the puckered type of planes but with a depletion of the protruding Co atoms. The surface energy of the determined surface model was calculated using DFT, and it takes a rather low value of $1.09\phantom{\rule{4pt}{0ex}}{\mathrm{J}/\mathrm{m}}^{2}$. The results for the atomic relaxation of surface planes found by SXRD or DFT were in excellent agreement. This work opens up additional perspectives for the comprehension of related quasicrystalline surfaces.

Coxeter groups, quiver mutations and geometric manifolds

We construct finite volume hyperbolic manifolds with large symmetry groups. The construction makes use of the presentations of finite Coxeter groups provided by Barot and Marsh and involves mutations of quivers and diagrams defined in the theory of cluster algebras. We generalize our construction by assigning to every quiver or diagram of finite or affine type a CW-complex with a proper action of a finite (or affine) Coxeter group. These CW-complexes undergo mutations agreeing with mutations of quivers and diagrams. We also generalize the construction to quivers and diagrams originating from unpunctured surfaces and orbifolds.