Thick braneworlds generated by a non-minimally coupled scalar field and a Gauss-Bonnet term: conditions for localization of gravity

We consider warped five-dimensional thick braneworlds with four-dimensional Poincar\'e invariance originated from bulk scalar matter non-minimally coupled to gravity plus a Gauss-Bonnet term. The background field equations as well as the perturbed equations are investigated. A relationship between 4D and 5D Planck masses is studied in general terms. By imposing finiteness of the 4D Planck mass and regularity of the geometry, the localization properties of the tensor modes of the perturbed geometry are analyzed to first order, for a wide class of solutions. In order to explore the gravity localization properties for this model, the normalizability condition for the lowest level of the tensor fluctuations is analyzed. It is found that for the examined class of solutions, gravity in 4 dimensions is recovered if the curvature invariants are regular and the 4D Planck mass is finite. It turns out that both the addition of the Gauss-Bonnet term and the non-minimal coupling between the scalar field and gravity {\it reduce} the value of the 4D Planck mass compared to its value when the scalar field and gravity are minimally coupled and the Gauss-Bonnet term is absent. The above discussed analysis depends on the explicit form of the scalar field (through its non-minimal coupling to gravity), making necessary the construction of explicit solutions in order to get results in closed form, and is illustrated with some examples which constitute smooth generalizations of the so-called Randall-Sundrum braneworld model. These solutions were obtained by making use of a detailed {\it singular perturbation theory} procedure with respect to the non-minimal coupling parameter between the scalar field and gravity, a difficult task that we managed to perform in such a way that all the physically meaningful conditions for the localization of gravity are fully satisfied. From the obtained...Comment: 27 pages, uses iopart, 12 figure

PENGUKURAN KALORI PADA TEPUNG SAGU TEPUNG TERIGU DAN GULA DENGAN MENGGUNAKAN BOM KALORIMETER

RINGKASAN Kalorimetri yaitu cara penentuan kalor reaksi dengan menggunakan calorimeter. Kalorimeter terbagi menjadi dua, yaitu calorimeter bom dan calorimeter sederhana. Kalorimeter bom adalah alat yang digunakan untuk mengukur jumlah kalor (nilai kalori) yang dibebaskan pada pembakaran sempurna (dalam O2 berlebih) suatu senyawa, bahan makanan, bahan bakar atau khusus digunakan untuk menentukan kalor dari reaksi-reaksi pembakaran. Kalorimeter makanan biasanya dipakai untuk mengukur kalor reaksi yang reaksinya berlangsung dalam fase larutan (misalnya reaksi netralisasi asam–basa/netralisasi, pelarutan dan pengendapan). Calorimeter sederhana dilakukan pada tekanan tetap yang dibuat dari gelas stirofoam. Uji kinerja alat bom calorimeter ini dilakukan pada pengukuran nilai kalori bahan makanan. Pengukuran nilai kalori ini dilakukan untuk tepung sagu,tepung terigu,dan gula. Untuk membandingkan energy yang mampu dihasilkan oleh masing-masing bahan makanan tersebut, maka dilakukan pengukuran nilai kalori yang dikandung tepung sagu,tepung terigu,dan gula Hasil yang diperoleh dari praktikum menyatakan bahwa dari ketiga macam jenis bahan makanan tersebut yaitu tepung sagu,tepung terigu,dan gula, nilai kalori tertinggi terkandung pada gula. artinya bahwa Gula merupakan bahan makanan yang berkalori tinggi di bandingkan dengan tepung sagu dan tepung terigu,Gula paling berpotensi menyebabkan obesitas,yang kemungkinan besar dapat menyabakkan penyakit Diabete

A de Sitter tachyon thick braneworld

Among the multiple 5D thick braneworld models that have been proposed in the last years, in order to address several open problems in modern physics, there is a specific one involving a tachyonic bulk scalar field. Delving into this framework, a thick braneworld with a cosmological background induced on the brane is here investigated. The respective field equations --- derived from the model with a warped 5D geometry --- are highly non-linear equations, admitting a non-trivial solution for the warp factor and the tachyon scalar field as well, in a de Sitter 4D cosmological background. Moreover, the non-linear tachyonic scalar field, that generates the brane in complicity with warped gravity, has the form of a kink-like configuration. Notwithstanding, the non-linear field equations restricting character does not allow one to easily find thick brane solutions with a decaying warp factor which leads to the localization of 4D gravity and other matter fields. We derive such a thick brane configuration altogether in this tachyon-gravity setup. When analyzing the spectrum of gravity fluctuations in the transverse traceless sector, the 4D gravity is shown to be localized due to the presence of a {\it single} zero mode bound state, separated by a continuum of massive Kaluza-Klein (KK) modes by a mass gap. It contrasts with previous results, where there is a KK massive bound excitation providing no clear physical interpretation. The mass gap is determined by the scale of the metric parameter $H$. Finally, the corrections to Newton's law in this model are computed and shown to decay exponentially. It is in full compliance to corrections reported in previous results (up to a constant factor) within similar braneworlds with induced 4D de Sitter metric, despite the fact that the warp factor and the massive modes have a different form.Comment: 16 pages in latex, 4 figures, JCAP format, title changed, presentation improved, figures added, discussion on stability include

A de Sitter tachyonic braneworld revisited

Within the framework of braneworlds, several interesting physical effects can be described in a wide range of energy scales, starting from high-energy physics to cosmology and low-energy physics. An usual way to generate a thick braneworld model relies in coupling a bulk scalar field to higher dimensional warped gravity. Quite recently, a novel braneworld was generated with the aid of a tachyonic bulk scalar field, having several remarkable properties. It comprises a regular and stable solution that contains a relevant 3--brane with de Sitter induced metric, arising as an exact solution to the 5D field equations, describing the inflationary eras of our Universe. Besides, it is {\it asymptotically flat}, despite of the presence of a negative 5D cosmological constant, which is an interesting feature that contrasts with most of the known, asymptotically either dS or AdS models. Moreover, it encompasses a graviton spectrum with a single massless bound state, accounting for 4D gravity localized on the brane, separated from the continuum of Kaluza-Klein massive graviton modes by a mass gap that makes the 5D corrections to Newton's law to decay exponentially. Finally, gauge, scalar and fermion fields are also shown to be localized on this braneworld. In this work, we show that this tachyonic braneworld allows for a nontrivial solution with a vanishing 5D cosmological constant that preserves all the above mentioned remarkable properties with a less amount of parameters, constituting an important contribution to the construction of a realistic cosmological braneworld model.Comment: 13 pages and 2 figure