A Novel Solution to the Gravitino Problem

In a general phenomenological model with local supersymmetry, the amount of massive gravitinos produced in early universe tends to violate the known dark matter density bound by many orders of magnitude. This problem is absent in the recently proposed non-linear supergravity model in the brane world scenario in Type IIB string theory, where we (i.e., the standard model of strong and electroweak interactions) live in a stack of $\overline{\rm D3}$-branes (i.e., anti-D3-branes) that span the 3 large spatial dimensions. These $\overline{\rm D3}$-branes break supersymmetry. As an open string mode in there, the Goldstino to be eaten by the gravitino is present only inside the $\overline{\rm D3}$-branes. So, although a gravitino can be massive (e.g., $\overline{m}_{3/2} \ge 100$ GeV) inside the $\overline{\rm D3}$-branes, it is (almost) massless outside the $\overline{\rm D3}$-branes. It follows that the massive gravitinos produced inside the $\overline{\rm D3}$-branes will be pushed out of the $\overline{\rm D3}$-branes, analogous to the Meissner effect for the massive photons in super-conductors. As a result, the massive gravitinos will be depleted so the gravitino problem is absent.Comment: 13 pages, 1 figure, 2 table

The Role of Mediodorsal Thalamus in Temporal Differentiation of Reward-Guided Actions

The mediodorsal thalamus (MD) is a crucial component of the neural network involved in the learning and generation of goal-directed actions. A series of experiments reported here examined the contributions of MD to the temporal differentiation of reward-guided actions. In Experiment 1, we trained rats on a discrete-trial, fixed-criterion temporal differentiation task, in which only lever presses exceeding a threshold duration value were rewarded. Pre-training MD lesions impaired temporal differentiation of action duration, by increasing the dispersion of the duration distribution. Post-training MD lesions also impaired differentiation, but by reducing the average emitted press durations, thus shifting the distribution without increasing the dispersion. In Experiment 2, we trained rats to space their lever pressing above criterion inter-press-intervals in order to earn rewards. Both pre-training and post-training MD lesions impaired the differentiation of inter-press-intervals. These results show that MD plays an important role in the acquisition and expression of action differentiation

Baryon Number Violating Rate as A Function of the Proton-Proton Collision Energy

The baryon-number violation (BV) happens in the standard electroweak model. According to the Bloch-wave picture, the BV event rate shall be significantly enhanced when the proton-proton collision center of mass (COM) energy goes beyond the sphaleron barrier height $E_{\rm sph}\simeq 9.0\,{\rm TeV}$. Here we compare the BV event rates at different COM energies, using the Bloch-wave band structure and the CT18 parton distribution function data, with the phase space suppression factor included. As an example, the BV cross-section at 25 TeV is 4 orders of magnitude bigger than its cross-section at 13 TeV.Comment: 7 pages, 6 figures, and 4 table

Rb-Sr, Sm-Nd and Ar-Ar isotopic systematics of Antarctic nakhlite Yamato 000593

sotopic analysis of the newly found Antarctic nakhlite Yamato (Y) 000593 yields a Rb-Sr age of 1.30±0.02Ga with an initial ^(87)Sr/^(86)Sr of 0.702525±0.000027, a Sm-Nd age of 1.31±0.03Ga with an initial ε_(Nd) of + 16.0±0.2 and an Ar-Ar isochron age of <=1.36Ga. The concordancy of these three ages and Rb-Sr and Sm-Nd initial isotopic signatures strongly suggest that Y000593 crystallized from low Rb/Sr, light REE-depleted source materials ～1.31Ga ago. The crystallization age of Y000593 is compared with the age data of non-Antarctic nakhlites (Nakhla, Governador Valadares, Lafayette and Northwest Africa 998) and Chassigny. The initial Sr and Nd isotopic signatures suggest that Lafayette and Y000593 were co-magmatic or at least came from very similar magmas. Cosmogenic ^(36)Ar concentrations in Y000593 resemble those in other nakhlites. The similarities in crystallization and ejection ages and in petrologic features suggest the nakhlites were derived from similar source regions, and launch pairing of nakhlites and Chassigny. The Rb-Sr data for Y000593 show that the isotopic system is disturbed by pre-terrestrial alteration of olivine. Although many of the acid-leached residues of mineral fractions fall along the 1.30Ga Rb-Sr isochron, leached olivine does not. This indicates the lack of isotopic equilibrium between the olivine fractions and the secondary alteration phases. A tie-line between two olivine leachates provides a calculated "age" of 650±80Ma with an initial ^(87)Sr/^(86)Sr of ～0.70465, which gives a hint for the isotopic signatures of local brine as well as the timing of an aqueous alteration event on the Martian surface

Ultra Light Axionic Dark Matter: Galactic Halos and Implications for Observations with Pulsar Timing Arrays

The cold dark matter (CDM) paradigm successfully explains the cosmic structure over an enormous span of redshifts. However, it fails when probing the innermost regions of dark matter halos and the properties of the Milky Way’s dwarf galaxy satellites. Moreover, the lack of experimental detection of Weakly Interacting Massive Particle (WIMP) favors alternative candidates such as light axionic dark matter that naturally arise in string theory. Cosmological N-body simulations have shown that axionic dark matter forms a solitonic core of size of ≃150 pc in the innermost region of the galactic halos. The oscillating scalar field associated to the axionic dark matter halo produces an oscillating gravitational potential that induces a time dilation of the pulse arrival time of ≃400 ns/(m B /10 −22 eV) for pulsar within such a solitonic core. Over the whole galaxy, the averaged predicted signal may be detectable with current and forthcoming pulsar timing array telescopes.IDM acknowledges financial support from University of the Basque Country UPV/EHU under the program "Convocatoria de contratacion para la especializacion de personal investigador doctor en la UPV/EHU 2015", from the Spanish Ministerio de Economia y Competitividad through research project FIS2010-15492, and from the Basque Government through research project IT-956-16. RL is supported by the Spanish Ministry of Economy and Competitiveness through research projects FIS2010-15492 and Consolider EPI CSD2010-00064, and by the University of the Basque Country UPV/EHU under program UFI 11/55. IDM and RL also acknowledge support from the COST Action CA1511 Cosmology and Astrophysics Network for Theoretical Advances and Training Actions (CANTATA). TJB acknowledges generous hospitality from the Institute for Advanced Studies in Hong Kong and helpful conversations with Nick Kaiser and Kfir Blum. SHHT is supported by CRF Grant HKUST4/CRF/13G and GRF 16305414 issued by the Research Grants Council (RGC) of the Government of the Hong Kong SAR. Chipbond Technology Corporation is acknowledged for donating the GPU cluster with which this work was conducted. This work was supported in part by the National Science Council of Taiwan under grants NSC100-2112-M-002-018-MY3 and NSC99-2112-M-002-009-MY