[1212.1661] Cross comparison and modelling of Goldman Sachs, Morgan Stanley, JPMorgan Chase, Bank of America, and Franklin Resources:
"We have studied statistical characteristics of five share price time series. For each stock price, we estimated a best fit quantitative model for the monthly closing price as based on the decomposition into two defining consumer price indices selected from a large set of CPIs. It was found that there are two pairs of similar models (Bank of America/Morgan Stanley and Goldman Sachs/JPMorgan Chase) with a standalone model for Franklin Resources. From each pair, one can choose the company with the highest return depending on the future evolution of defining CPIs"
'via Blog this'
Thursday, April 30, 2015
Goldman and IDG Put $50 Million to Work in a Bitcoin Company - NYTimes.com
Goldman and IDG Put $50 Million to Work in a Bitcoin Company - NYTimes.com:
"Goldman Sachs is becoming the first major bank to make a significant investment in a Bitcoin-focused company, giving a vote of confidence to the embattled virtual currency."
'via Blog this'
"Goldman Sachs is becoming the first major bank to make a significant investment in a Bitcoin-focused company, giving a vote of confidence to the embattled virtual currency."
'via Blog this'
Wednesday, April 29, 2015
76 Semesters (Personal) by Paul Krugman
Blogging has been limited lately, because it’s the end of term and I have a lot of things to do (plus get ready for an extended visit to Oxford starting soon.) But today was a bit of a personal landmark. Regular readers may know that I’m taking early retirement from Princeton — which has been a wonderful place for me, but I’m just overextended — and taking up an appointment at CUNY Graduate Center, one with limited teaching.
And this morning I gave my last class — my last class at Princeton, and if we don’t count the graduate seminars I’ll give at CUNY, we could say my last class period.
I started as an assistant professor at Yale in the fall of 1977. So I’ve been a college professor for 76 semesters. It’s been a great ride. But time to move on.
Can Bitcoin Conquer Argentina? - NYTimes.com
Can Bitcoin Conquer Argentina? - NYTimes.com:
"Dante Castiglione stalked through the doors of a glass-walled office tower on the edge of downtown Buenos Aires, just a few hundred feet from the old port district. In the crowded elevator, he shook his head and muttered under his breath about the stresses of the day and his profession. “I swear, this job can kill me,” he said, his eyes cast downward."
'via Blog this'
"Dante Castiglione stalked through the doors of a glass-walled office tower on the edge of downtown Buenos Aires, just a few hundred feet from the old port district. In the crowded elevator, he shook his head and muttered under his breath about the stresses of the day and his profession. “I swear, this job can kill me,” he said, his eyes cast downward."
'via Blog this'
[1504.07236] New blazars from the cross-match of recent multi-frequency catalogs
[1504.07236] New blazars from the cross-match of recent multi-frequency catalogs:
"Blazars are radio-loud active galactic nuclei well known for their non thermal emission spanning a wide range of frequencies. The Roma-BZCAT is, to date, the most comprehensive list of these sources. We performed the cross-match of several catalogs obtained from recent surveys at different frequencies to search for new blazars. We cross-matched the 1st Swift-XRT Point Source catalog with the spectroscopic sample of the 9th Data Release of the Sloan Digital Sky Survey. Then, we performed further cross-matches with the catalogs corresponding to the Faint Images of the Radio Sky at Twenty cm survey and to the AllWISE Data release, focusing on sources with infrared colors similar to those of confirmed γ-ray blazars included in the Second Fermi-LAT catalog. As a result, we obtained a preliminary list of objects with all the elements needed for a proper blazar classification according to the prescriptions of the Roma-BZCAT. We carefully investigated additional properties such as their morphology and the slope of their spectral energy distribution in the radio domain, the features shown in their optical spectrum, and the luminosity in the soft X rays to exclude generic active galactic nuclei and focus on authentic blazar-like sources. At the end of our screening we obtained a list of 15 objects with firmly established blazar properties."
'via Blog this'
"Blazars are radio-loud active galactic nuclei well known for their non thermal emission spanning a wide range of frequencies. The Roma-BZCAT is, to date, the most comprehensive list of these sources. We performed the cross-match of several catalogs obtained from recent surveys at different frequencies to search for new blazars. We cross-matched the 1st Swift-XRT Point Source catalog with the spectroscopic sample of the 9th Data Release of the Sloan Digital Sky Survey. Then, we performed further cross-matches with the catalogs corresponding to the Faint Images of the Radio Sky at Twenty cm survey and to the AllWISE Data release, focusing on sources with infrared colors similar to those of confirmed γ-ray blazars included in the Second Fermi-LAT catalog. As a result, we obtained a preliminary list of objects with all the elements needed for a proper blazar classification according to the prescriptions of the Roma-BZCAT. We carefully investigated additional properties such as their morphology and the slope of their spectral energy distribution in the radio domain, the features shown in their optical spectrum, and the luminosity in the soft X rays to exclude generic active galactic nuclei and focus on authentic blazar-like sources. At the end of our screening we obtained a list of 15 objects with firmly established blazar properties."
'via Blog this'
U.S. Attacks in Afghanistan Go Beyond White House’s Pledges - NYTimes.com
U.S. Attacks in Afghanistan Go Beyond White House’s Pledges - NYTimes.com:
"KABUL, Afghanistan — Months after President Obama formally declared that the United States’ long war against the Taliban was over in Afghanistan, the American military is regularly conducting airstrikes against low-level insurgent forces and sending Special Operations troops directly into harm’s way under the guise of “training and advising.”"
'via Blog this'
"KABUL, Afghanistan — Months after President Obama formally declared that the United States’ long war against the Taliban was over in Afghanistan, the American military is regularly conducting airstrikes against low-level insurgent forces and sending Special Operations troops directly into harm’s way under the guise of “training and advising.”"
'via Blog this'
Tuesday, April 28, 2015
Big Mac Test Shows Job Market Is Not Working to Distribute Wealth - NYTimes.com
Big Mac Test Shows Job Market Is Not Working to Distribute Wealth - NYTimes.com:
"Some 15 years ago, searching for a consistent way to compare wages of equivalent workers across the world, Orley Ashenfelter, an economics professor at Princeton University, came upon McDonald’s."
'via Blog this'
"Some 15 years ago, searching for a consistent way to compare wages of equivalent workers across the world, Orley Ashenfelter, an economics professor at Princeton University, came upon McDonald’s."
'via Blog this'
Income Inequality Is Costing the U.S. on Social Issues - NYTimes.com
Income Inequality Is Costing the U.S. on Social Issues - NYTimes.com:
"Thirty-five years ago, the United States ranked 13th among the 34 industrialized nations that are today in the Organization for Economic Cooperation and Development in terms of life expectancy for newborn girls. These days, it ranks 29th."
'via Blog this'
"Thirty-five years ago, the United States ranked 13th among the 34 industrialized nations that are today in the Organization for Economic Cooperation and Development in terms of life expectancy for newborn girls. These days, it ranks 29th."
'via Blog this'
VSPs versus MSEs - NYTimes.com
VSPs versus MSEs - NYTimes.com:
"Simon Wren-Lewis tries to put his finger on something I’ve also been trying to get at — the sharp difference between what influential people think they know about economics and what people who actually study the economy think they know. My take may be slightly different at the margin, but I do believe that it’s important."
'via Blog this'
"Simon Wren-Lewis tries to put his finger on something I’ve also been trying to get at — the sharp difference between what influential people think they know about economics and what people who actually study the economy think they know. My take may be slightly different at the margin, but I do believe that it’s important."
'via Blog this'
[1502.00225] Power-law correlations in finance-related Google searches, and their cross-correlations with volatility and traded volume: Evidence from the Dow Jones Industrial components
[1502.00225] Power-law correlations in finance-related Google searches, and their cross-correlations with volatility and traded volume: Evidence from the Dow Jones Industrial components:
"We study power-law correlations properties of the Google search queries for Dow Jones Industrial Average (DJIA) component stocks. Examining the daily data of the searched terms with a combination of the rescaled range and rescaled variance tests together with the detrended fluctuation analysis, we show that the searches are in fact power-law correlated with Hurst exponents between 0.8 and 1.1. The general interest in the DJIA stocks is thus strongly persistent. We further reinvestigate the cross-correlation structure between the searches, traded volume and volatility of the component stocks using the detrended cross-correlation and detrending moving-average cross-correlation coefficients. Contrary to the universal power-law correlations structure of the related Google searches, the results suggest that there is no universal relationship between the online search queries and the analyzed financial measures. Even though we confirm positive correlation for a majority of pairs, there are several pairs with insignificant or even negative correlations. In addition, the correlations vary quite strongly across scales."
'via Blog this'
"We study power-law correlations properties of the Google search queries for Dow Jones Industrial Average (DJIA) component stocks. Examining the daily data of the searched terms with a combination of the rescaled range and rescaled variance tests together with the detrended fluctuation analysis, we show that the searches are in fact power-law correlated with Hurst exponents between 0.8 and 1.1. The general interest in the DJIA stocks is thus strongly persistent. We further reinvestigate the cross-correlation structure between the searches, traded volume and volatility of the component stocks using the detrended cross-correlation and detrending moving-average cross-correlation coefficients. Contrary to the universal power-law correlations structure of the related Google searches, the results suggest that there is no universal relationship between the online search queries and the analyzed financial measures. Even though we confirm positive correlation for a majority of pairs, there are several pairs with insignificant or even negative correlations. In addition, the correlations vary quite strongly across scales."
'via Blog this'
2% Inflation Rate Target Is Questioned as Fed Policy Panel Prepares to Meet - NYTimes.com
2% Inflation Rate Target Is Questioned as Fed Policy Panel Prepares to Meet - NYTimes.com:
"WASHINGTON — The cardinal rule of central banking, in the United States and in most other advanced industrial nations, is that annual inflation should run around 2 percent."
'via Blog this'
"WASHINGTON — The cardinal rule of central banking, in the United States and in most other advanced industrial nations, is that annual inflation should run around 2 percent."
'via Blog this'
The Trader as Scapegoat - NYTimes.com
The Trader as Scapegoat - NYTimes.com:
"A BRITISH trader, Navinder Singh Sarao, is facing extradition to the United States. Federal prosecutors accuse him of having significantly contributed to the “flash crash” of May 6, 2010, in which major American stock markets plunged dramatically in a matter of minutes. Prosecutors also say that he manipulated prices on the Chicago Mercantile Exchange for years by “spoofing,” or placing orders that he intended to cancel before they were filled."
'via Blog this'
"A BRITISH trader, Navinder Singh Sarao, is facing extradition to the United States. Federal prosecutors accuse him of having significantly contributed to the “flash crash” of May 6, 2010, in which major American stock markets plunged dramatically in a matter of minutes. Prosecutors also say that he manipulated prices on the Chicago Mercantile Exchange for years by “spoofing,” or placing orders that he intended to cancel before they were filled."
'via Blog this'
Monday, April 27, 2015
Nobody Said That - NYTimes.com
Nobody Said That - NYTimes.com:
"Imagine yourself as a regular commentator on public affairs — maybe a paid pundit, maybe an supposed expert in some area, maybe just an opinionated billionaire. You weigh in on a major policy initiative that’s about to happen, making strong predictions of disaster. The Obama stimulus, you declare, will cause soaring interest rates; the Fed’s bond purchases will “debase the dollar” and cause high inflation; the Affordable Care Act will collapse in a vicious circle of declining enrollment and surging costs."
'via Blog this'
"Imagine yourself as a regular commentator on public affairs — maybe a paid pundit, maybe an supposed expert in some area, maybe just an opinionated billionaire. You weigh in on a major policy initiative that’s about to happen, making strong predictions of disaster. The Obama stimulus, you declare, will cause soaring interest rates; the Fed’s bond purchases will “debase the dollar” and cause high inflation; the Affordable Care Act will collapse in a vicious circle of declining enrollment and surging costs."
'via Blog this'
Sunday, April 26, 2015
[1504.06336] Electric fields and quantum wormholes
[1504.06336] Electric fields and quantum wormholes:
"Electric fields can thread a classical Einstein-Rosen bridge. Maldacena and Susskind have recently suggested that in a theory of dynamical gravity the entanglement of ordinary perturbative quanta should be viewed as creating a quantum version of an Einstein-Rosen bridge between the particles, or a "quantum wormhole". We demonstrate within low-energy effective field theory that there is a precise sense in which electric fields can also thread such quantum wormholes. We define a non-perturbative "wormhole susceptibility" that measures the ease of passing an electric field through any sort of wormhole. The susceptibility of a quantum wormhole is suppressed by powers of the U(1) gauge coupling relative to that for a classical wormhole but can be made numerically equal with a sufficiently large amount of entangled matter."
'via Blog this'
"Electric fields can thread a classical Einstein-Rosen bridge. Maldacena and Susskind have recently suggested that in a theory of dynamical gravity the entanglement of ordinary perturbative quanta should be viewed as creating a quantum version of an Einstein-Rosen bridge between the particles, or a "quantum wormhole". We demonstrate within low-energy effective field theory that there is a precise sense in which electric fields can also thread such quantum wormholes. We define a non-perturbative "wormhole susceptibility" that measures the ease of passing an electric field through any sort of wormhole. The susceptibility of a quantum wormhole is suppressed by powers of the U(1) gauge coupling relative to that for a classical wormhole but can be made numerically equal with a sufficiently large amount of entangled matter."
'via Blog this'
Ancient Collision Made Nepal Earthquake Inevitable - NYTimes.com
Ancient Collision Made Nepal Earthquake Inevitable - NYTimes.com:
"More than 25 million years ago, India, once a separate island on a quickly sliding piece of the Earth’s crust, crashed into Asia. The two land masses are still colliding, pushed together at a speed of 1.5 to 2 inches a year. The forces have pushed up the highest mountains in the world, in the Himalayas, and have set off devastating earthquakes."
'via Blog this'
"More than 25 million years ago, India, once a separate island on a quickly sliding piece of the Earth’s crust, crashed into Asia. The two land masses are still colliding, pushed together at a speed of 1.5 to 2 inches a year. The forces have pushed up the highest mountains in the world, in the Himalayas, and have set off devastating earthquakes."
'via Blog this'
Friday, April 24, 2015
In Battle Between Strong Dollar and Cheap Gas, the Strong Dollar Is Winning - NYTimes.com
In Battle Between Strong Dollar and Cheap Gas, the Strong Dollar Is Winning - NYTimes.com:
"There were two big shifts in global markets in the second half of 2014 that looked likely to shape how the American economy would perform in 2015.
"
'via Blog this'
"There were two big shifts in global markets in the second half of 2014 that looked likely to shape how the American economy would perform in 2015.
"
'via Blog this'
Grunsfeld
The Advanced Technology Large-Aperture Space Telescope (ATLAST) is a set of
mission concepts for the next generation of UVOIR space observatory with a
primary aperture diameter in the 8-m to 16-m range that will allow us to
perform some of the most challenging observations to answer some of our most
compelling questions, including "Is there life elsewhere in the Galaxy?" We
have identified two different telescope architectures, but with similar optical
designs, that span the range in viable technologies. The architectures are a
telescope with a monolithic primary mirror and two variations of a telescope
with a large segmented primary mirror. This approach provides us with several
pathways to realizing the mission, which will be narrowed to one as our
technology development progresses. The concepts invoke heritage from HST and
JWST design, but also take significant departures from these designs to
minimize complexity, mass, or both.
Our report provides details on the mission concepts, shows the extraordinary scientific progress they would enable, and describes the most important technology development items. These are the mirrors, the detectors, and the high-contrast imaging technologies, whether internal to the observatory, or using an external occulter. Experience with JWST has shown that determined competitors, motivated by the development contracts and flight opportunities of the new observatory, are capable of achieving huge advances in technical and operational performance while keeping construction costs on the same scale as prior great observatories.
arXiv
Our report provides details on the mission concepts, shows the extraordinary scientific progress they would enable, and describes the most important technology development items. These are the mirrors, the detectors, and the high-contrast imaging technologies, whether internal to the observatory, or using an external occulter. Experience with JWST has shown that determined competitors, motivated by the development contracts and flight opportunities of the new observatory, are capable of achieving huge advances in technical and operational performance while keeping construction costs on the same scale as prior great observatories.
arXiv
Thursday, April 23, 2015
U.S. Maps Areas of Increased Earthquakes From Human Activity - NYTimes.com
U.S. Maps Areas of Increased Earthquakes From Human Activity - NYTimes.com:
"In its first comprehensive assessment of earthquakes believed to be caused by human activity, the United States Geological Survey released a map on Thursday identifying 17 regions with significant levels of seismic movement triggered mostly from oil and gas operations."
'via Blog this'
"In its first comprehensive assessment of earthquakes believed to be caused by human activity, the United States Geological Survey released a map on Thursday identifying 17 regions with significant levels of seismic movement triggered mostly from oil and gas operations."
'via Blog this'
Wednesday, April 22, 2015
New York City’s Environment Program Will Focus on Income Inequality - NYTimes.com
New York City’s Environment Program Will Focus on Income Inequality - NYTimes.com:
"In his most sweeping bid yet to apply a focus on income inequality across the municipal spectrum, Mayor Bill de Blasio of New York on Wednesday will introduce a reimagined take on the city’s ambitious environmental program, PlaNYC."
'via Blog this'
"In his most sweeping bid yet to apply a focus on income inequality across the municipal spectrum, Mayor Bill de Blasio of New York on Wednesday will introduce a reimagined take on the city’s ambitious environmental program, PlaNYC."
'via Blog this'
Tuesday, April 21, 2015
In Atomic Labs Across U.S., a Race to Stop Iran - NYTimes.com
In Atomic Labs Across U.S., a Race to Stop Iran - NYTimes.com:
"WASHINGTON — When diplomats at the Iran talks in Switzerland pummeled Department of Energy scientists with difficult technical questions — like how to keep Iran’s nuclear plants open but ensure that the country was still a year away from building a bomb — the scientists at times turned to a secret replica of Iran’s nuclear facilities built deep in the forests of Tennessee."
'via Blog this'
"WASHINGTON — When diplomats at the Iran talks in Switzerland pummeled Department of Energy scientists with difficult technical questions — like how to keep Iran’s nuclear plants open but ensure that the country was still a year away from building a bomb — the scientists at times turned to a secret replica of Iran’s nuclear facilities built deep in the forests of Tennessee."
'via Blog this'
Monday, April 20, 2015
Teachers’ Unions Reasserting Themselves With Push Against Standardized Testing
By KATE TAYLOR and MOTOKO RICH
In Florida, the teachers’ union has lobbied to limit the use of standardized tests, and the governor last week signed a bill that limits the number of hours students can spend taking them.
The union in New Jersey financed an advertising campaign in which a grim-faced father talks about his son crying because of tests.
And in New York, where local unions have worked closely with parent groups that oppose testing, the president of the state union went so far as to urge parents to opt out of the annual tests, which began last week.
After several years in which teachers’ unions have been hammered on the issue of tenure, have lost collective bargaining rights in some states and have seen their evaluations increasingly tied to student scores, they have begun, with some success, to reassert themselves using a bread-and-butter issue: the annual tests given to elementary and middle school students in every state.
The teachers’ push on testing comes as Congress is debating how to revise the 2001 No Child Left Behind law, which requires that schools demonstrate annual progress on test scores and prescribed measures for schools deemed failing, from mandatory tutoring to closing. Lawmakers are considering a bill that removes the most punitive consequences for schools and makes clear that states do not have to use test scores to evaluate teachers.
Critics of the campaigns against testing, including many state and local education officials, say the unions are not acting out of concern for children but are trying to undercut efforts to institute tougher evaluations. They argue that annual testing is critical for tracking how effectively schools are educating poor and minority students and that evaluations based only on subjective criteria like observations typically fail to identify weak teachers.
“It’s right at the point when we finally actually have the kind of improved tests that so many folks petitioned for and advocated for for years,” said Jonah Edelman, the chief executive of Stand for Children, an advocacy group that supports charter schools and teacher evaluations that incorporate student test scores. He added that the organization supports legislation to reduce unnecessary testing, but “encouraging parents to opt out is not an effort to reduce overtesting. It’s an effort to undermine accountability.”
The amount of time students spend preparing for and taking standardized tests has been a political issue for years. It has become particularly acute as states have switched to more difficult tests designed to align with the Common Core, academic standards adopted by more than 40 states and spurred in part by the federal government.
Nelson Lichtenstein, a labor historian at the University of California, Santa Barbara, said the unions’ strategy on testing follows years in which they have been under assault, by conservative leaders and by the bipartisan education-reform movement that has painted unions as a central obstacle to improving schools.
Scott Walker, the Wisconsin governor and possible presidential candidate, stoked national attention when he stripped collective-bargaining rights from most public-sector unions, including teachers.
But testing, Mr. Lichtenstein said, offers unions a way to join forces both with parents who object to testing and with Republicans who oppose the Common Core standards as a federalization of education.
“It is a powerful issue, by virtue of the fact that the right is also against it,” he said.
Secky Fascione, director of organizing for the National Education Association, the largest nationwide teachers’ union, said reining in testing was the union’s top organizing priority. In the past month, Ms. Fascione said, chapters in 27 states have organized against testing, including holding rallies; petition drives; showings of “Standardized,” a documentary critical of testing; and sessions telling parents they have a right to keep their children from taking tests, as tens of thousands of parents around the country have done.
“Does it give us a platform?” said Karen E. Magee, the president of the New York State United Teachers. “Absolutely.”
Her union began agitating more vocally against testing after Gov. Andrew M. Cuomo, denouncing an evaluation system in which 96 percent of teachers received good ratings, proposed increasing the weight of test scores in teacher evaluations. The union argued that it was not fair to make test scores so big a part of a teacher’s rating because many factors outside the classroom can influence scores.
Although the State Legislature ultimately settled on a compromise, the union seemed to win the public relations battle. Polls found that more voters sided with the teachers’ union over education policies than with Mr. Cuomo.
Ms. Magee urged parents to opt out of the tests to subvert the rating system, though state education officials said districts would have to come up with alternative methods of evaluating teachers who did not have enough test scores.
The union followed up with robocalls to its members, encouraging those with children in the grades that take the tests, third through eighth, to keep their own children out of the exams.
Although official numbers have not yet been released, it is likely that many more parents in New York State are keeping their children out of the tests than did last year, particularly in wealthy suburbs and neighborhoods of New York City. One advocacy group estimated, based on news and parent reports and information from local officials, that more than 150,000 students, or more than 15 percent of the testing grades, sat out the English exams last week. The math exams are being given this week.
Some education officials have tried to rein in teachers who have advocated for opting out. In Rochester, a district official asked principals to identify teachers who had sent emails or made phone calls to parents encouraging them to opt out, or who “you have evidence as utilizing their classrooms as ‘political soapboxes.’” TheFlorida education commissioner warned that “certain willful opt-out behaviors may warrant disciplinary action” against teachers.
Around the country, individual union leaders are approaching the issue with varying levels of fervor. Lily Eskelsen Garcia, president of the National Education Association, and Randi Weingarten, president of the other major teachers’ group, the American Federation of Teachers, say they support parents’ right to opt their children out of standardized tests but have not gone as far as Ms. Magee and some local chapters in encouraging parents to do so.
In Kentucky, where the education commissioner has said parents do not have the right to opt their children out of tests, the state union is not pushing back. “We have to have an assessment of standards,” said Stephanie Winkler, president of the Kentucky Education Association. She added that parents could not “pick and choose” which parts of public education they wanted their children to participate in.
But union leaders have faced pressure within their ranks to take a harder line. A national group of teachers claiming more than 50,000 members has criticized both of the main unions for supporting the Common Core and is pushing for the abandonment of all standardized tests.
Before a meeting last week of the New York City teachers’ union, the United Federation of Teachers, members of New Action, a caucus within the union, handed out a pamphlet that encouraged teachers to “stand in solidarity with parents who want to opt their children out of this needless overtesting.” But the union’s president, Michael Mulgrew, warned members to leave the decision to parents and not to talk them into refusing the tests.
At a time of ambivalence about teachers’ unions, the anti-testing agenda has “taken the heat off of them,” said Jeffrey M. Stonecash, professor emeritus of political science at Syracuse University. He warned, however, that the unions should be careful to control their message about testing and its connection to measuring success.
“The teachers’ unions are in a terrible situation,” he said, “because on the one hand they want to argue that expectations are too high. But the question that lurks behind that is, ‘So you mean teachers don’t have any impact on students?’”
[1403.0576] Dark Matter as a Trigger for Periodic Comet Impacts
[1403.0576] Dark Matter as a Trigger for Periodic Comet Impacts:
"Although statistical evidence is not overwhelming, possible support for an approximately 35 million year periodicity in the crater record on Earth could indicate a nonrandom underlying enhancement of meteorite impacts at regular intervals. A proposed explanation in terms of tidal effects on Oort cloud comet perturbations as the Solar System passes through the galactic midplane is hampered by lack of an underlying cause for sufficiently enhanced gravitational effects over a sufficiently short time interval and by the time frame between such possible enhancements. We show that a smooth dark disk in the galactic midplane would address both these issues and create a periodic enhancement of the sort that has potentially been observed. Such a disk is motivated by a novel dark matter component with dissipative cooling that we considered in earlier work. We show how to evaluate the statistical evidence for periodicity by input of appropriate measured priors from the galactic model, justifying or ruling out periodic cratering with more confidence than by evaluating the data without an underlying model. We find that, marginalizing over astrophysical uncertainties, the likelihood ratio for such a model relative to one with a constant cratering rate is 3.0, which moderately favors the dark disk model. Our analysis furthermore yields a posterior distribution that, based on current crater data, singles out a dark matter disk surface density of approximately 10 solar masses per square parsec. The geological record thereby motivates a particular model of dark matter that will be probed in the near future."
'via Blog this'
"Although statistical evidence is not overwhelming, possible support for an approximately 35 million year periodicity in the crater record on Earth could indicate a nonrandom underlying enhancement of meteorite impacts at regular intervals. A proposed explanation in terms of tidal effects on Oort cloud comet perturbations as the Solar System passes through the galactic midplane is hampered by lack of an underlying cause for sufficiently enhanced gravitational effects over a sufficiently short time interval and by the time frame between such possible enhancements. We show that a smooth dark disk in the galactic midplane would address both these issues and create a periodic enhancement of the sort that has potentially been observed. Such a disk is motivated by a novel dark matter component with dissipative cooling that we considered in earlier work. We show how to evaluate the statistical evidence for periodicity by input of appropriate measured priors from the galactic model, justifying or ruling out periodic cratering with more confidence than by evaluating the data without an underlying model. We find that, marginalizing over astrophysical uncertainties, the likelihood ratio for such a model relative to one with a constant cratering rate is 3.0, which moderately favors the dark disk model. Our analysis furthermore yields a posterior distribution that, based on current crater data, singles out a dark matter disk surface density of approximately 10 solar masses per square parsec. The geological record thereby motivates a particular model of dark matter that will be probed in the near future."
'via Blog this'
[1409.2981] Thoughts on opportunities from high-energy nuclear collisions
[1409.2981] Thoughts on opportunities from high-energy nuclear collisions:
"This document summarizes thoughts on opportunities from high-energy nuclear collisions."
'via Blog this'
"This document summarizes thoughts on opportunities from high-energy nuclear collisions."
'via Blog this'
[1504.03388] The behaviour of dark matter associated with 4 bright cluster galaxies in the 10kpc core of Abell 3827
[1504.03388] The behaviour of dark matter associated with 4 bright cluster galaxies in the 10kpc core of Abell 3827:
"Galaxy cluster Abell 3827 hosts the stellar remnants of four almost equally bright elliptical galaxies within a core of radius 10kpc. Such corrugation of the stellar distribution is very rare, and suggests recent formation by several simultaneous mergers. We map the distribution of associated dark matter, using new Hubble Space Telescope imaging and VLT/MUSE integral field spectroscopy of a gravitationally lensed system threaded through the cluster core. We find that each of the central galaxies retains a dark matter halo, but that (at least) one of these is spatially offset from its stars. The best-constrained offset is 1.62+/-0.48kpc, where the 68% confidence limit includes both statistical error and systematic biases in mass modelling. Such offsets are not seen in field galaxies, but are predicted during the long infall to a cluster, if dark matter self-interactions generate an extra drag force. With such a small physical separation, it is difficult to definitively rule out astrophysical effects operating exclusively in dense cluster core environments - but if interpreted solely as evidence for self-interacting dark matter, this offset implies a cross-section sigma/m=(1.7+/-0.7)x10^{-4}cm^2/g x (t/10^9yrs)^{-2}, where t is the infall duration."
'via Blog this'
"Galaxy cluster Abell 3827 hosts the stellar remnants of four almost equally bright elliptical galaxies within a core of radius 10kpc. Such corrugation of the stellar distribution is very rare, and suggests recent formation by several simultaneous mergers. We map the distribution of associated dark matter, using new Hubble Space Telescope imaging and VLT/MUSE integral field spectroscopy of a gravitationally lensed system threaded through the cluster core. We find that each of the central galaxies retains a dark matter halo, but that (at least) one of these is spatially offset from its stars. The best-constrained offset is 1.62+/-0.48kpc, where the 68% confidence limit includes both statistical error and systematic biases in mass modelling. Such offsets are not seen in field galaxies, but are predicted during the long infall to a cluster, if dark matter self-interactions generate an extra drag force. With such a small physical separation, it is difficult to definitively rule out astrophysical effects operating exclusively in dense cluster core environments - but if interpreted solely as evidence for self-interacting dark matter, this offset implies a cross-section sigma/m=(1.7+/-0.7)x10^{-4}cm^2/g x (t/10^9yrs)^{-2}, where t is the infall duration."
'via Blog this'
Greece on the Brink
“Don’t you think they want us to fail?” That’s the question I kept hearing during a brief but intense visit to Athens. My answer was that there is no “they” — that Greece does not, in fact, face a solid bloc of implacable creditors who would rather see default and exit from the euro than let a leftist government succeed, that there’s more good will on the other side of the table than many Greeks suppose.
But you can understand why Greeks see things that way. And I came away from the visit fearing that Greece and Europe may suffer a terrible accident, an unnecessary rupture that will cast long shadows over the future.
The story so far: At the end of 2009 Greece faced a crisis driven by two factors: High debt, and inflated costs and prices that left the country uncompetitive.
Europe responded with loans that kept the cash flowing, but only on condition that Greece pursue extremely painful policies. These included spending cuts and tax hikes that, if imposed on the United States, would amount to $3 trillion a year. There were also wage cuts on a scale that’s hard to fathom, with average wages down 25 percent from their peak.
These immense sacrifices were supposed to produce recovery. Instead, the destruction of purchasing power deepened the slump, creating Great Depression-level suffering and a huge humanitarian crisis. On Saturday I visited a shelter for the homeless, and was told heartbreaking tales of a health care system in collapse: patients turned away from hospitals because they couldn’t pay the 5 euro entrance fee, sent away without needed medicine because cash-starved clinics had run out, and more.
It has been an endless nightmare, yet Greece’s political establishment, determined to stay within Europe and fearing the consequences of default and exit from the euro, stayed with the program year after year. Finally, the Greek public could take no more. As creditors demanded yet more austerity — on a scale that might well have pushed the economy down by another 8 percent and driven unemployment to 30 percent — the nation voted in Syriza, a genuinely left-wing (as opposed to center-left) coalition, which has vowed to change the nation’s course. Can Greek exit from the euro be avoided?
Yes, it can. The irony of Syriza’s victory is that it came just at the point when a workable compromise should be possible.
The key point is that exiting the euro would be extremely costly and disruptive in Greece, and would pose huge political and financial risks for the rest of Europe. It’s therefore something to be avoided if there’s a halfway decent alternative. And there is, or should be.
By late 2014 Greece had managed to eke out a small “primary” budget surplus, with tax receipts exceeding spending, excluding interest payments. That’s all that creditors can reasonably demand, since you can’t keep squeezing blood from a stone. Meanwhile, all those wage cuts have made Greece competitive on world markets — or would make it competitive if some stability can be restored.
The shape of a deal is therefore clear: basically, a standstill on further austerity, with Greece agreeing to make significant but not ever-growing payments to its creditors. Such a deal would set the stage for economic recovery, perhaps slow at the start, but finally offering some hope.
But right now that deal doesn’t seem to be coming together. Maybe it’s true, as the creditors say, that the new Greek government is hard to deal with. But what do you expect when parties that have no previous experience in governing take over from a discredited establishment? More important, the creditors are demanding things — big cuts in pensions and public employment — that a newly elected government of the left simply can’t agree to, as opposed to reforms like an improvement in tax enforcement that it can. And the Greeks, as I suggested, are all too ready to see these demands as part of an effort either to bring down their government or to make their country into an example of what will happen to other debtor countries if they balk at harsh austerity.
To make things even worse, political uncertainty is hurting tax receipts, probably causing that hard-earned primary surplus to evaporate. The sensible thing, surely, is to show some patience on that front: if and when a deal is reached, uncertainty will subside and the budget should improve again. But in the pervasive atmosphere of distrust, patience is in short supply.
It doesn’t have to be this way. True, avoiding a full-blown crisis would require that creditors advance a significant amount of cash, albeit cash that would immediately be recycled into debt payments. But consider the alternative. The last thing Europe needs is for fraying tempers to bring on yet another catastrophe, this one completely gratuitous.
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