Band gaps in the relaxed linear micromorphic continuum

In this note we show that the relaxed linear micromorphic model recently proposed by the authors can be suitably used to describe the presence of band-gaps in metamaterials with microstructures in which strong contrasts of the mechanical properties are present (e.g. phononic crystals and lattice structures). This relaxed micromorphic model only has 6 constitutive parameters instead of 18 parameters needed in Mindlin- and Eringen-type classical micromorphic models. We show that the onset of band-gaps is related to a unique constitutive parameter, the Cosserat couple modulus $\mu_{c}$ which starts to account for band-gaps when reaching a suitable threshold value. The limited number of parameters of our model, as well as the specific effect of some of them on wave propagation can be seen as an important step towards indirect measurement campaigns

Measurement of the Gravity-Field Curvature by Atom Interferometry

We present the first direct measurement of the gravity-field curvature based on three conjugated atom interferometers. Three atomic clouds launched in the vertical direction are simultaneously interrogated by the same atom interferometry sequence and used to probe the gravity field at three equally spaced positions. The vertical component of the gravity-field curvature generated by nearby source masses is measured from the difference between adjacent gravity gradient values. Curvature measurements are of interest in geodesy studies and for the validation of gravitational models of the surrounding environment. The possibility of using such a scheme for a new determination of the Newtonian constant of gravity is also discussed.Comment: 5 pages, 3 figure

Sensitivity limits of a Raman atom interferometer as a gravity gradiometer

We evaluate the sensitivity of a dual cloud atom interferometer to the measurement of vertical gravity gradient. We study the influence of most relevant experimental parameters on noise and long-term drifts. Results are also applied to the case of doubly differential measurements of the gravitational signal from local source masses. We achieve a short term sensitivity of 3*10^(-9) g/Hz^(-1/2) to differential gravity acceleration, limited by the quantum projection noise of the instrument. Active control of the most critical parameters allows to reach a resolution of 5*10^(-11) g after 8000 s on the measurement of differential gravity acceleration. The long term stability is compatible with a measurement of the gravitational constant G at the level of 10^(-4) after an integration time of about 100 hours.Comment: 19 pages, 20 figure

Quantum test of the equivalence principle for atoms in superpositions of internal energy eigenstates

The Einstein Equivalence Principle (EEP) has a central role in the understanding of gravity and space-time. In its weak form, or Weak Equivalence Principle (WEP), it directly implies equivalence between inertial and gravitational mass. Verifying this principle in a regime where the relevant properties of the test body must be described by quantum theory has profound implications. Here we report on a novel WEP test for atoms. A Bragg atom interferometer in a gravity gradiometer configuration compares the free fall of rubidium atoms prepared in two hyperfine states and in their coherent superposition. The use of the superposition state allows testing genuine quantum aspects of EEP with no classical analogue, which have remained completely unexplored so far. In addition, we measure the Eotvos ratio of atoms in two hyperfine levels with relative uncertainty in the low $10^{-9}$, improving previous results by almost two orders of magnitude.Comment: Accepted for publication in Nature Communicatio

Komunikasi Mitigasi Bencana oleh BPBD Provinsi Bengkulu pada Masyarakat di Daerah Aliran Sungai Lemau

AbstrakKeberadaan Badan Penanggulangan Bencana Daerah di Provinsi Bengkulu memiliki peranan yang sangat penting dalam upaya mitigasi bencana dikarenakan Bengkulu merupakan wilayah rentan terjadi bencana. Salah satu potensi bencana yang menjadi perhatian besar di provinsi Bengkulu yakni banjir. Oleh karena itu penelitian terkait pola komunikasi bencana yang dilakukan terhadap masyarkat di sekitar daerah aliran sungai Lemau yang mana merupakan wilayah rentan terdampak banjir perlu untuk dianalisis dan dievaluasi. Penelitian ini dilakukan dengan metode observasi dan wawancara. Observasi yang dilakukan yakni berupa pengamatan terhadap media komunikasi yang digunakan Badan Penanggulangan Bencana Daerah Provinsi Bengkulu yakni media sosial (facebook dan instagram). Wawancara dilakukan kepada Kepala Bidang Pra-Bencana BPBD Provinsi Bengkulu. Temuan dalam penelitian ini menunjukkan bahwa pola komunikasi yang dilakukan Badan Penanggulangan Bencana Daerah Provinsi Bengkulu dalam hal mitigasi bencana berupa koordinasi antar satuan kerja pemerintah daerah. Sedangkan komunikasi dengan memanfaatkan media sosial belum terfokus pada upaya mitigasi bencana melainkan kegiatan ceremonial instansi tersebut. AbstractThe existence of the Bengkulu Province Regional Disaster Management Agency has a very important role in disaster mitigation efforts because Bengkulu is a disaster-prone area. One of the potential disasters that is of great concern in Bengkulu province is flooding. Therefore, research related to disaster communication patterns carried out on the community around the Lemau river basin, which is a vulnerable area affected by floods, needs to be analyzed and evaluated. This research was conducted by observation and interview methods. The observations made were in the form of observations on the communication media used by the Regional Disaster Management Agency of Bengkulu Province, namely social media (Facebook and Instagram). The interview was conducted with the Head of the Pre-Disaster Division of BPBD Bengkulu Province. The findings in this study showed that the communication pattern carried out by the Regional Disaster Management Agency of Bengkulu Province in terms of disaster mitigation in the form of coordination between local government work units. At the same time, communication by utilizing social media has not been focused on disaster mitigation efforts but rather on ceremonial activities of the agency

Atom Interferometry with the Rb Blue Transitions

We demonstrate a novel scheme for Raman-pulse and Bragg-pulse atom interferometry based on the $5\mathrm{S} - 6\mathrm{P}$ blue transitions of $^{87}$Rb that provides an increase by a factor $\sim 2$ of the interferometer phase due to accelerations with respect to the commonly used infrared transition at 780 nm. A narrow-linewidth laser system generating more than 1 W of light in the 420-422 nm range was developed for this purpose. Used as a cold-atom gravity gradiometer, our Raman interferometer attains a stability to differential acceleration measurements of $1\times10^{-8}$ $g$ at 1 s and $2\times 10^{-10}$ $g$ after 2000 s of integration time. When operated on first-order Bragg transitions, the interferometer shows a stability of $6\times10^{-8}$ g at 1 s, averaging to $1\times10^{-9}$ g after 2000 s of integration time. The instrument sensitivity, currently limited by the noise due to spontaneous emission, can be further improved by increasing the laser power and the detuning from the atomic resonance. The present scheme is attractive for high-precision experiments as, in particular, for the determination of the Newtonian gravitational constant

Atmospheric fluctuations below 0.1 Hz during drift-scan solar diameter measurements

Measurements of the power spectrum of the seeing in the range 0.001-1 Hz have been performed in order to understand the criticity of the transits' method for solar diameter monitoring.Comment: 3 pages, 3 figures, proc. of the Fourth French-Chinese meeting on Solar Physics Understanding Solar Activity: Advances and Challenges, 15 - 18 November, 2011 Nice, Franc

New apparatus design for high-precision measurement ofG with atom interferometry

We propose a new scheme for an improved determination of the Newtonian gravitational constant G and evaluate it by numerical simulations. Cold atoms in free fall are probed by atom interferometry measurements to characterize the gravitational field generated by external source masses. Two source mass configurations having different geometry and using different materials are compared to identify an optimized experimental setup for the G measurement. The effects of the magnetic fields used to manipulate the atoms and to control the interferometer phase are also characterized