Exoplanet Characterization by Multi-Observatory Transit Photometry with TESS and CHEOPS

Space-based photometric surveys have discovered large numbers of planets transiting other stars, but these observe in a single band-pass and yield only the planet radius, orbital period, and transit duration. Information on the masses, compositions, and any atmospheres of these planets requires additional observations from the ground or space. The Transiting Exoplanet Survey Satellite (TESS) will yield thousands of planets around bright stars suitable for such follow-up. In the absence of spectroscopy or spectrophotometry from space, observations through the different pass-bands of multiple space telescopes provide some spectral information useful for identifying false positive signals, distinguishing between reflected light and thermal emission from hot Jupiters, and detecting Rayleigh scattering by planetary atmospheres. We calculated the expected difference in transit depths measured by the TESS and Characterizing Exoplanets Satellites (CHEOPS) missions, which will be more sensitive to redder and bluer optical wavelengths, respectively. The difference due to companion or background stars is small (<3% for main sequence companions) and likely to be negligible and undetectable. For only a few "hot" Jupiters, can combined photometry disambiguate between the reflected and thermal signals from planets. However, Rayleigh scattering by hazy atmospheres with particles sizes near 0.04 $\mu$m and at pressure altitudes above ~1 mbar can be detected for ~100 transiting planets, assuming every planet has such an atmosphere. Hazes with this characteristic particle size do not obscure observations at longer (near-infrared) wavelengths; CHEOPS follow-up of TESS-detected planets could thus identify candidates suitable for further study with the James Webb Space Telescope.Comment: MNRAS, in pres

EVOLUTION OF DOLLAR/EURO EXCHANGE RATE BEFORE AND AFTER THE BIRTH OF EURO AND POLICY IMPLICATIONS

One possible consequence of the establishment of the Euro is a challenge to the hegemony of the US dollar as the predominant international currency. No other currency has been able to rival the international role of the national currency of the US since World War II. The fact that the unipolar international monetary system can be unstable in the presence of large shocks opens a window of opportunity for the Euro to promote systemic stability. The present study pursues this conjecture by, first, exploring with cointegration and ECM techniques the interdependence between the dynamics of the Dollar/Euro exchange rate and economic fundamentals in the context of a monetary exchange rate model. Identification of the key determinants of the value of the Euro informs our analysis of the policy stance of the European Central Bank regarding the long-run global role of the Euro. Secondly, we explore whether the opportunity for a prominent systemic role of the Euro has been realized by examining the impact of the Euro on the global financial market.Euro, Exchange rate, Monetary model, Cointegration

pH-triggered phase inversion and separation of hydrophobised bacterial cellulose stabilised Pickering emulsions

The pH-triggered transitional phase behaviour of Pickering emulsions stabilised by hydrophobised bacterial cellulose (BC) is reported in this work. Neat BC was esterified with acetic (C2–), hexanoic (C6–) and dodecanoic (C12–) acids, respectively. We observed that C6– and C12–BC stabilised emulsions exhibited a pH-triggered reversible transitional phase separation. Water-in-toluene emulsions containing of 60 vol.% dispersed phase stabilised by C6– and C12–BC were produced at pH 5. Lowering the pH of the aqueous phase to 1 did not affect the emulsion type. Increasing the pH to 14, however, caused the emulsions to phase separate. This phase separation was caused by electrostatic repulsion between modified BC due to dissociable acidic surface groups at high pH, which lowered the surface coverage of the water droplets by modified BC. When the pH was re-adjusted to 1 again, w/o emulsions re-formed for C6– and C12–BC stabilised emulsions. C2–BC stabilised emulsions, on the other hand, underwent an irreversible pH-triggered transitional phase separation and inversion. This difference in phase behaviour between C2–BC and C6–/C12–BC was attributed to the hydrolysis of the ester bonds of C2–BC at high pH. This hypothesis is in good agreement with the measured degree of surface substitution (DSS) of modified BC after the pH-triggered experiments. The DSS of C2–BC decreased by 20% whilst the DSS remained constant for C6– and C12–BC

Bulk matter fields on two-field thick branes

In this paper we obtain a new solution of a brane made up of a scalar field coupled to a dilaton. There is a unique parameter $b$ in the solution, which decides the distribution of the energy density and will effect the localization of bulk matter fields. For free vector fields, we find that the zero mode can be localized on the brane. And for vector fields coupled with the dilaton via $\text{e}^{\tau\pi}F_{MN}F^{MN}$, the condition for localizing the zero mode is $\tau\geq-\sqrt{b/3}$ with $0-1/\sqrt{3b}$ with $b>1$, which includes the case $\tau=0$. While the zero mode for free Kalb-Ramond fields can not be localized on the brane, if only we introduce a coupling between the Kalb-Ramond fields and the dilaton via $\text{e}^{\zeta \pi}H_{MNL}H^{MNL}$. When the coupling constant satisfies $\zeta>1/\sqrt{3b}$ with $b\geq1$ or $\zeta>\frac{2-b}{\sqrt{3b}}$ with $0<b<1$, the zero mode for the KR fields can be localized on the brane. For spin half fermion fields, we consider the coupling $\eta\bar{\Psi}\text{e}^{\lambda \pi}\phi\Psi$ between the fermions and the background scalars with positive Yukawa coupling $\eta$. The effective potentials for both chiral fermions have three types of shapes decided by the relation between the dilaton-fermion coupling constant $\lambda$ and the parameter $b$. For $\lambda\leq-1/\sqrt{3b}$, the zero mode of left-chiral fermion can be localized on the brane. While for $\lambda>-1/\sqrt{3b}$ with $b>1$ or $-1/\sqrt{3b}<\lambda<-\sqrt{b/3}$ with $0<b\leq1$, the zero mode for left-chiral fermion also can be localized.Comment: 22 pages, 8 figures, improved version, accepted by Physical Review

Study of Λb→Λ(ϕ,η(′))\Lambda_b\to \Lambda (\phi,\eta^{(\prime)}) and Λb→ΛK+K−\Lambda_b\to \Lambda K^+K^- decays

We study the charmless two-body $\Lambda_b\to \Lambda (\phi,\eta^{(\prime)})$ and three-body $\Lambda_b\to \Lambda K^+K^-$ decays. We obtain ${\cal B}(\Lambda_b\to \Lambda\phi)=(3.53\pm 0.24)\times 10^{-6}$ to agree with the recent LHCb measurement. However, we find that ${\cal B}(\Lambda_b\to \Lambda(\phi\to)K^+ K^-)=(1.71\pm 0.12)\times 10^{-6}$ is unable to explain the LHCb observation of ${\cal B}(\Lambda_b\to\Lambda K^+ K^-)=(15.9\pm 1.2\pm 1.2\pm 2.0)\times 10^{-6}$, which implies the possibility for other contributions, such as that from the resonant $\Lambda_b\to K^- N^*,\,N^*\to\Lambda K^+$ decay with $N^*$ as a higher-wave baryon state. For $\Lambda_b\to \Lambda \eta^{(\prime)}$, we show that ${\cal B}(\Lambda_b\to \Lambda\eta,\,\Lambda\eta^\prime)= (1.47\pm 0.35,1.83\pm 0.58)\times 10^{-6}$, which are consistent with the current data of $(9.3^{+7.3}_{-5.3},<3.1)\times 10^{-6}$, respectively. Our results also support the relation of ${\cal B}(\Lambda_b\to \Lambda\eta) \simeq {\cal B}(\Lambda_b\to\Lambda\eta^\prime)$, given by the previous study.Comment: 8 pages, 1 figure, revised version accepted by EPJ

A Naturally Minute Quantum Correction to the Cosmological Constant Descended from the Hierarchy

We demonstrate that an extremely small but positive quantum correction, or the Casimir energy, to the cosmological constant can arise from a massive bulk fermion field in the Randall-Sundrum model. Specifically, a cosmological constant doubly descended from the Planck-electroweak hierarchy and as minute as the observed dark energy scale can be naturally achieved without fine-tuning of the bulk fermion mass. To ensure the stabilization of the system, we discuss two stabilization mechanisms under this setup. It is found that the Goldberger-Wise mechanism can be successfully introduced in the presence of a massive bulk fermion, without spoiling the smallness of the quantum correction.Comment: 5 page

Non-leptonic two-body weak decays of Λc(2286)\Lambda_c(2286)

We study the non-leptonic two-body weak decays of $\Lambda_c^+(2286)\to {\bf B}_n M$ with ${\bf B}_n$ ($M$) representing as the baryon (meson) states. Based on the $SU(3)$ flavor symmetry, we can describe most of the data reexamined by the BESIII Collaboration with higher precisions. However, our result of ${\cal B}(\Lambda_c^+ \to p\pi^0)=(5.6\pm 1.5)\times 10^{-4}$ is larger than the current experimental limit of $3\times10^{-4}$ (90\% C.L.) by BESIII. In addition, we find that ${\cal B}(\Lambda_c^+ \to \Sigma^+ K^0)=(8.0\pm 1.6)\times 10^{-4}$, ${\cal B}(\Lambda_c^+ \to \Sigma^+ \eta^\prime)=(1.0^{+1.6}_{-0.8})\times 10^{-2}$, and ${\cal B}(\Lambda_c^+ \to p \eta^\prime)=(12.2^{+14.3}_{-\,\,\,8.7})\times 10^{-4}$, which are accessible to the BESIII experiments.Comment: 12 pages, 1 figure, revised version accepted by PL

A Non-isothermal Theory for Interpreting Sodium Lines in Transmission Spectra of Exoplanets

We present a theory for interpreting the sodium lines detected in transmission spectra of exoplanetary atmospheres. Previous analyses employed the isothermal approximation and dealt only with the transit radius. By recognising the absorption depth and the transit radius as being independent observables, we develop a theory for jointly interpreting both quantities, which allows us to infer the temperatures and number densities associated with the sodium lines. We are able to treat a non-isothermal situation with a constant temperature gradient. Our novel diagnostics take the form of simple-to-use algebraic formulae and require measurements of the transit radii (and their corresponding absorption depths) at line center and in the line wing for both sodium lines. We apply our diagnostics to the HARPS data of HD 189733b, confirm the upper atmospheric heating reported by Huitson et al. (2012), derive a temperature gradient of $0.4376 \pm 0.0154$ K km$^{-1}$ and find densities $\sim 1$ to $10^4$ cm$^{-3}$.Comment: Accepted by ApJ Letters. 6 pages, 3 figure