Exacerbating the cosmological constant problem with interacting dark energy

Future cosmological surveys will probe the expansion history of the universe and constrain phenomenological models of dark energy. Such models do not address the fine-tuning problem of the vacuum energy, i.e. the cosmological constant problem (c.c.p.), but can make it spectacularly worse. We show that this is the case for 'interacting dark energy' models in which the masses of the dark matter states depend on the dark energy sector. If realised in nature, these models have far-reaching implications for proposed solutions to the c.c.p. that require the number of vacua to exceed the fine-tuning of the vacuum energy density. We show that current estimates of the number of flux vacua in string theory, $N_{\rm vac} \sim {\cal O}(10^{272,000})$, is far too small to realise certain simple models of interacting dark energy \emph{and} solve the cosmological constant problem anthropically. These models admit distinctive observational signatures that can be targeted by future gamma-ray observatories, hence making it possible to observationally rule out the anthropic solution to the cosmological constant problem in theories with a finite number of vacua.Comment: v2: 6 pages, 2 figures; extended discussion of observational prospects (conclusions unchanged); accepted to PR

Using HINODE/Extreme-Ultraviolet Imaging Spectrometer to confirm a seismologically inferred coronal temperature

The Extreme-Ultraviolet Imaging Spectrometer on board the HINODE satellite is used to examine the loop system described in Marsh et al. (2009) by applying spectroscopic diagnostic methods. A simple isothermal mapping algorithm is applied to determine where the assumption of isothermal plasma may be valid, and the emission measure locii technique is used to determine the temperature profile along the base of the loop system. It is found that, along the base, the loop has a uniform temperature profile with a mean temperature of 0.89 +- 0.09 MK which is in agreement with the temperature determined seismologically in Marsh et al. (2009), using observations interpreted as the slow magnetoacoustic mode. The results further strengthen the slow mode interpretation, propagation at a uniform sound speed, and the analysis method applied in Marsh et al. (2009). It is found that it is not possible to discriminate between the slow mode phase speed and the sound speed within the precision of the present observations

Demand and Supply Factors in the Feed Grain Market: Effects on Corn Producers

Demand and Price Analysis,

ECONOMIC FACTORS DETERMINING CHANGES IN DRESSED WEIGHTS OF LIVE CATTLE AND HOGS

Livestock dressed weights have experienced significant trends and volatility which affect wholesale production of red meats. An econometric model was used to estimate the impact of relative prices and technology on cattle and hog average dressed weights. For fed steers and heifers, the economic incentives affecting placement weights and weight added in feedlots were considered. Results indicate quarterly dressed weights of steers and heifers respond to contemporaneous profitability ratios and to lagged feeder prices, the effects being highly inelastic. Cow dressed weights also responded while hog dressed weights did not respond to profitability ratios. Technology changes may have accounted for about 83% of dressed weight growth for steers and about 62% for hogs from 1980-97.Livestock Production/Industries,

U.S. BEEF TRADE AND PRICE RELATIONSHIPS WITH JAPAN, CANADA, AND MEXICO

U.S. live cattle and beef trade has increased substantially since the mid-1980s. Total beef imports (cattle and beef, dressed weight) increased from 2.51 billion pounds in 1985 to 3.89 billion pounds in 1998. Total beef exports (cattle and beef, dressed weight) increased from 0.42 billion pounds to 2.38 billion pounds over the same period. Consequently, net imports declined by 0.58 billion pounds. On a value basis, U.S. net beef exports (value of total beef exports less the value of total beef imports) has become considerably less negative, increasing by 88 percent from 1980 to 1998. The overall improvement in the U.S. beef trade was characterized, however, by different trade impacts with the major export customers and import suppliers. These countries are Japan, Canada, Mexico, South Korea, Australia, and New Zealand. Trade relationships and beef price effects in this article mainly address those of the first three countries. From 1990 to 1998, U.S. net imports of live cattle and beef (carcass weight) for all countries declined from 9.2 percent to 5.2 percent of total U.S. beef supplies. Given the average market price for that period and the coefficient of price flexibility, this decline implied an increase in nominal slaughter steer price of $4.00/cwt. However, this price effect was offset by other factors in the domestic market, such as large competitive production, increasing dressed weights, increasing wholesale-retail margins, and a decrease in consumer beef demand. Japan constitutes about 54 percent of the export market for U.S. beef. This country has been the fastest growing export market for high-value cuts of U.S. beef; quantities exported increased by 101 percent from 1990 to 1998. Strong economic growth (until 1997), trade liberalization, and changes in dietary preferences account for most of the increase. The result of these expanding exports, as a percentage of total beef disposition, was an increase in slaughter steer price of$1.70/cwt. U.S. beef and live cattle trade with Mexico has improved considerably (until recent import tariffs on U.S. beef); that is, net beef exports were negative at 357 million pounds in 1990 but became positive at 200 million pounds in 1998. Declines in imported Mexican cattle and increases in U.S. beef exports account for the change. Mexico currently accounts for nearly 20 percent of U.S. beef exports. The result of erasing the trade deficit over the 1990 to 1998 period was an increase in slaughter price of $2.12/cwt. The U.S.-Mexican net trade position in beef and live cattle may remain volatile in the future, however. The U.S. net beef trade position with Canada has declined considerably. Including trade in live cattle and beef, net imports from Canada increased from 2.7 percent to 5.2 percent of U.S. beef supplies from 1990 to 1998. In general, imports (cattle and beef) have significantly increased, while exports (cattle and beef) have increased little over this period. Reasons for the increased deficit include Canadian grain policies and feedlot expansion, U.S. excess capacity in meatpacking, a strong U.S. dollar and intercountry price differentials. The result was a reduction in U.S. slaughter price of$2.55/cwt. Economists, however, consider the U.S.-Canadian beef markets to be highly integrated. Thus, reducing the trade deficit may have little impact on U.S. slaughter price. Overall, U.S. trade in live cattle and beef has not reached the same importance as that of grain. Nevertheless, U.S. export and import quantities measured as a percentage of supplies or disposition imply that producer price effects are not zero. Domestic factors of beef dressed weights, red meat and poultry production, beef margins, feed costs, and consumer beef demand still dominate the price determination picture. The provisional tariff imposed on Canadian exports of live cattle, but recently removed by the U.S. International Trade Commission (ITC), would have slightly increased U.S. price and decreased Canadian price. But with compensating Canadian carcasses and beef entering the U.S. market, and increased slaughter costs, the gains may have been nullified.International Relations/Trade,

Evaluation of Beef Promotion Expenditures Under the U.S. Beef Checkoff Program

Agricultural and Food Policy,

Feed Grain Volatility and Effects on Feeder Cattle Producers

Production Economics,

Distribution of Cost Efficiencies in the Beef Marketing Channel

Marketing,

Hyperinflation generalised: from its attractor mechanism to its tension with the `swampland conjectures'

In negatively curved field spaces, inflation can be realised even in steep potentials. Hyperinflation invokes the `centrifugal force' of a field orbiting the hyperbolic plane to sustain inflation. We generalise hyperinflation by showing that it can be realised in models with any number of fields ($N_f\geq2$), and in broad classes of potentials that, in particular, don't need to be rotationally symmetric. For example, hyperinflation can follow a period of radial slow-roll inflation that undergoes geometric destabilisation, yet this inflationary phase is not identical to the recently proposed scenario of `side-tracked inflation'. We furthermore provide a detailed proof of the attractor mechanism of (the original and generalised) hyperinflation, and provide a novel set of characteristic, explicit models. We close by discussing the compatibility of hyperinflation with observations and the recently much discussed `swampland conjectures'. Observationally viable models can be realised that satisfy either the `de Sitter conjecture' ($V'/V\gtrsim 1$) or the `distance conjecture' ($\Delta \phi \lesssim 1$), but satisfying both simultaneously brings hyperinflation in some tension with successful reheating after inflation. However, hyperinflation can get much closer to satisfying all of these criteria than standard slow-roll inflation. Furthermore, while the original model is in stark tension with the weak gravity conjecture, generalisations can circumvent this issue.Comment: 26 pages, 3 figure