first_imgSundaram Mutual Fund has launched a closed-end income scheme called Sundaram Fixed Term Plan – HT. The issue opened on Wednesday (Aug. 31) and will remain open till Thursday (Sept. 1).The scheme will have a duration of 1,100 days from the date of allotment of units to investors and will invest in debt and money market securities that would mature on or before the maturity of the scheme, according to the offer document.There are two options for investors under the scheme: growth and dividend payout (quarterly and half-yearly). The minimum investment is Rs. 5,000 and in multiples of Rs. 10 thereafter per application.There won’t be any buyback of units given that it is a closed-end scheme. “The Fund will not buy the units back till the maturity of the scheme. However, in order to provide the liquidity to the investors, the units of the Scheme are proposed to be listed on National Stock Exchange of India Limited (NSE) within 5 business days from the date of allotment,” the offer document disclosed.Other details of Sundaram Fixed Term Plan-HT:Entry load: NilExit Load: Not ApplicableDividend will be distributed at the discretion of the Trustee from the available distributable surplus, if any. The dividend when declared will be paid (subject of deduction of tax at source).Unitholders may choose to receive the redemption/dividend proceeds in any of the bank accounts, the details of which are registered with the AMC by specifying the necessary details in the “Bank Accounts Registration form”.Individuals, HUFs, Sole proprietor firms can register up to five bank accounts and other investors can register up to ten bank accounts in a folio.Sandeep Agarwal is the fund manager.On all working days, NAV will be computed (except in special circumstances detailed in the Statement of Additional Information/Scheme (NAV) Publication Information Document) and shall be published in at least two daily newspapers having circulation all over India and updated on the websites of Sundaram Asset Management.last_img read more

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first_imgMirza Fakhrul Islam Alamgir. File photoBangladesh Nationalist Party (BNP) on Saturday called upon the government to immediately intensify its diplomatic efforts to resolve the Rohingya crisis and force Myanmar to take back its citizens taken shelter in Bangladesh, reports UNB.Speaking at a discussion programme, BNP secretary general Mirza Fakhrul Islam Alamgir alleged that the current government has so far failed to take any right decision on Rohingya issues as it remains ‘enchained’.“You (govt) couldn’t take any correct decision on the Rohingya issue as you’re enchained. Even, you can’t take any decision on your own… the country’s people and we want the Rohingya crisis to be solved immediately,” he said.The BNP leader further said, “We also want the fleeing Rohingyas to be given shelter, food and healthcare. We demand the government strengthen its diplomatic efforts so that Rohingyas can be repatriated to their country with dignity.”BNP organised the programme at the Institution of Engineers, Bangladesh, marking the party’s 39th founding anniversary.Fakhrul came down hard on Awami League general secretary Obaidul Quader for his comment that BNP is doing ‘foul’ politics over Rohingya issue. “You’re accusing us of doing foul politics as we’re talking about the persecution on Rohingyas.”He said it is Awami League not BNP that has long been indulging in foul politics. “You’ve started doing such politics in 1972 by enacting the Special Power Act, snatching people’s rights, press freedom and establishing one-party politics the 4th amendment.”The BNP secretary general said their party is talking in favour of hapless Rohingyas who are being evicted from their houses, property and motherland as their party’ always does politics for people and humanity.He said though the Indonesian foreign minister and Turkish foreign minister and first lady visited Bangladesh over Rohingya problem, the government is playing a ‘silent’ role in resolving it.Criticising the government for what he said repressing their party men, Fakhrul said the government even obstructed their party’s Friday’s human chain programme on Rohingya issue at different parts of the country.“I would like to ask you why you fear us so much. We know you do it as you know you’ll lose your existence if BNP takes to the streets and joins the next election. We want to say the next election must be held under a non-party supportive government with the participation of all parties.Speaking at the programme, party standing committee member Khandaker Mosharraf Hossain said the government is conspiring to hold another Januar-5, 2014 like election by force keeping BNP out of it.He said the next polls must be held under a non-party supportive government so that people can exercise their right to franchise and all parties can take part in it.The BNP leader said their party chairperson Khaleda Zia will present the framework of the election-time supportive government once she returns home from London completing her medical treatment.Another BNP standing committee member Mirza Abbas said Indian Prime Minister Narendra Modi extended his support to Myanmar’s policy to eliminate Rohingya, sending out a message for Bangladesh government not to take any strong stance on Rohingya issue. “Awami League is now not talking anything in favour of Rohingyas.”He said the country’s people have got aggrieved over the government’s silence on Rohingya issue. “If necessary, we’ll call for a long march towards Myanmar. Our stance is clear we can’t allow the neighbouring country to kill people in such a manner.”last_img read more

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first_img Share Reynaldo Leal for The Texas TribuneJavier Alejandro Vindel-Rodriguez on the Brownsville Express International Bridge, where U.S. Customs and Border Patrol agents deterred asylum seekers like his family from crossing the border.In the weeks since President Donald Trump’s now-rescinded family separation policy created chaos and confusion across the country, the messages from his administration and prominent Republican members of Congress have been clear: Seek asylum legally at official ports of entry, and you won’t lose your kids. There may be armed Customs and Border Protection agents standing at the halfway points of bridges — but simply wait a few days, declare to them that you are seeking asylum, and you’ll get a fair shake.A recent Department of Homeland Security news release says it’s a “myth” that the agency “separates families who entered at the ports of entry and who are seeking asylum – even though they have not broken the law.” The release also says the agency “is [not] turning away asylum seekers at ports of entry.”But there’s ample evidence to suggest otherwise. Court records and individual cases discovered by The Texas Tribune indicate that a number of asylum-seekers who came to international bridges in Texas and California were separated from their children anyway — or were not able to cross the bridge at all after encountering armed Customs and Border Protection agents on the bridge. And experts argue there’s no basis to the government’s claim that there aren’t enough resources to process asylum-seekers.On top of that, experts say a quirk of U.S. immigration law might actually put people who try to seek asylum at the official ports of entry at a disadvantage to those who cross the border in other ways — such as wading across the Rio Grande. That’s because unlike people who cross the border illegally, asylum-seekers who come to ports of entry are not eligible to be bonded out of immigration detention by a judge; instead, officials with Immigration and Customs Enforcement (ICE) have total discretion over whether they can be released.“There’s no magic to the port of entry,” said Camilo Perez-Bustillo, who works at El Paso-based advocacy group the Hope Border Institute. “This idea that that’s the legal way to go … It’s fundamentally misleading.”This week Jennifer Harbury, an immigration lawyer based in the Rio Grande Valley, told the Tribune that she saw Mexican immigration officials standing at the foot of the bridge between Reynosa, Mexico, and McAllen and stopping people before they could begin to cross.“There’s two big guys in full dress standing right in front of the turnstile,” Harbury said. “They’ll walk up to you and … they just say, papers, please?”It’s not clear whether this is a widespread practice. Harbury said the immigration officials she saw wanted migrants to prove they had entered Mexico legally. If they couldn’t, she said, “they risk getting grabbed by the Mexican immigration people and deported.”Family separation said to go “beyond its lawful reach”At a recent roundtable in Weslaco, Texas’ Republican U.S. Sens. John Cornyn and Ted Cruz both expressed keen interest in what was happening at America’s international bridges. Cornyn specifically asked federal officials to confirm that asylum-seekers who came to the bridges were not doing anything illegal. The following day, he tweeted: “Asylum seekers that cross at ports of entry are not prosecuted” for entering the U.S. illegally — which should mean that they would not have been separated from their children.But the Hope Border Institute has documented cases of family separation at ports of entry that go back as far as December 2016 — just after Trump’s election. At that time, a woman named Eva, who said she faced death threats despite being in a witness protection program in Honduras, had asked for asylum with her husband and son at an El Paso port of entry. According to a reportreleased by the Institute in January, she “was immediately detained and separated from her family” and remained in detention more than a year later.Last September, Maria Vandelice de Bastos and her 16-year-old disabled grandson traveled from Brazil, were separated after arriving at the Santa Teresa Port of Entry in New Mexico and have not seen each other since, the Tribune reported recently. In May, a Guatemalan woman identified as M.G.U. showed up at a California port of entry with her three sons — ages 2, 6 and 13 — and even though she convinced officials that she had a credible fear of returning to Guatemala, her kids were taken away about two weeks later, according to a lawsuit filed by the advocacy group Texas RioGrande Legal Aid in June.And last November, according to a lawsuit filed by the ACLU, a Congolese woman called Ms. L. and her then-6-year-old daughter were separated at a California port of entry after seeking asylum from religious persecution.U.S. District Judge Dana Sabraw criticized the practice in a recent ruling on that lawsuit. “The parent has committed no crime,” she pointed out, adding, “Ms. L. is an example of this family separation practice expanding beyond its lawful reach, and she is not alone.” She went on to order the government to reunite separated families in the coming weeks.It’s not clear why these separations are happening, since none of the parents appear to have been prosecuted for entering the U.S. illegally. In the case of Ms. L., immigration officials initially claimed that they weren’t sure that she was actually the girl’s mother, the lawsuit documents say — which is another reason the Department of Homeland Security says it might decide to separate families who seek asylum at ports of entry.But Sabraw rejected the government’s argument: “Absent a finding the parent is unfit or presents a danger to the child, it is unclear why separation of Ms. L. [and her daughter] … would be necessary.”An ICE official said on Thursday that the agency does not release information on juveniles and referred a Tribune reporter to Customs and Border Protection. A CBP spokesman pointed the reporter to the news release the agency put out in June.Cornyn’s office did not respond to requests for comment. A Cruz staffer referred reporters to the comments he made at the Weslaco roundtable, in which he encouraged families to seek asylum the “right way” by going to ports of entry.A disadvantage in immigration detentionAs the Trump administration seeks to detain more and more people while their asylum cases are pending — even if they’ve never been charged with a criminal offense in the U.S. — asylum-seekers at ports of entry may actually be worse off than those who cross a different way.If people end up in immigration detention after they cross the border illegally between ports of entry — typically by crossing the Rio Grande or walking through desert — then ICE can set a bond for them (that’s the price they must pay for their release). Those detainees can challenge the bond before an immigration judge, and the judge can agree to release them with a lower bond or with no bond at all — although reports indicate it’s become harder for people to get released from immigration detention on bond.But for those who are detained after seeking asylum at a port of entry, bond is generally not an option, and an immigration judge can’t release them. Once they’re in immigration detention, they are only eligible for what’s called “parole” — temporary release from immigration detention — and that decision is up to ICE.Perez-Bustillo, of the Hope Border Institute, said that puts asylum-seekers who tried to cross the border the “right” way at a disadvantage. “When it comes to discretion of ICE … you’re totally helpless,” he said.A 2009 directive by the Obama administration gave immigration officials wide latitude to release people from detention on parole. But in 2017, the Trump administration told officials to use parole “sparingly”; a lawsuit filed by the ACLU over the issue claims that parole rates have since plummeted from 90 percent to close to zero.This week, a federal judge in Washington ordered the government to review parole decisions for a number of immigrant detainees who have been in detention for months or years. The government must release those detainees if they’re moving forward with their asylum cases and if they’re not a flight risk or a danger to the community, the ruling stated. But the decision only applies to five U.S. immigration offices across the country. El Paso is one of them, but Harlingen, located in the Rio Grande Valley, is not.Meanwhile, the longer people remain in immigration detention, the harder it is for them to truly pursue an asylum case. Making phone calls can be expensive, and detainees usually don’t have internet, so finding a lawyer is nearly impossible. And even if they manage to find one, they’re still at a major disadvantage.Ruby Powers, an immigration attorney based in Houston who recently interviewed about a dozen people at the Port Isabel detention center, said she prefers to meet with asylum-seeking clients multiple times. But that’s often not a luxury she can afford for clients in detention because visiting them is so time-consuming. She said she waited two hours in the Port Isabel facility just to get access to a room for the interviews she did recently.Experts cast doubt on “come back later” strategyTrump administration officials continue encouraging asylum-seekers to go to ports of entry and insist that no one is being turned away. “We are telling these people, look, we are full today … come back later,” explained David Higgerson, a field director for CBP, during last month’s roundtable discussion in Weslaco.He added that the agency has limited capacity and resources. A CBP agent might have to make a calculation such as, “I can probably handle a family of six. I cannot handle a family of 10,” he said.But Harbury said she’s represented multiple clients who were turned away at the port of entry outright. Not long after Trump was inaugurated in early 2017, Harbury said a woman from Guatemala was told to turn back at a Texas port of entry and later reported that she was kidnapped near the foot of the bridge on the Mexican side.The cartel members who kidnapped her demanded ransom, and the woman’s family took weeks to scrape together the money, Harbury said. When the cartel released her and she turned up at a Reynosa shelter, the staff called Harbury, who said she met the woman there and physically walked her across the bridge into the U.S.Lindsay M. Harris, co-director of the Immigration and Human Rights clinic at the University of the District of Columbia’s law school, said she doesn’t buy the argument that CBP doesn’t have the capacity to process all the asylum-seekers who show up at ports of entry.“If you just look at the manpower that CBP has … it’s just not a credible articulation of what’s going on,” she said. She also pointed out that the number of asylum-seekers has not suddenly skyrocketed since Trump’s election.In the federal fiscal year before Trump was elected, which ended in September 2016, the government received around 94,000 “credible fear claims” — a key step toward making an asylum request — and 24,500 of those were presented at ports of entry. The following year that number dropped to about 78,600, with 24,400 of them presented at ports of entry.On Monday, Selma Yznaga, an associate professor at the University of Texas – Rio Grande Valley, said she spent four hours on the Mexican side of the bridge between Matamoros and Brownsville. She said 13 asylum-seekers — three Cubans, four Hondurans and six people from African countries — were blocked from crossing the halfway point of the bridge by CBP officials.“They’re quite desperate,” she said. “It helps just to be there, to talk to them, to try to lift their spirits.”Two lawyers accompanied her, along with a humanitarian group from Matamoros, she said. The lawyers took down the asylum-seekers’ contact information so they could follow up once they were able to cross into the U.S.Yznaga said she has taken several such trips in the last two months.“The rules keep changing,” she said. At first, she felt she needed to explain to parents that they might be separated from their children. Now that Trump has signed an executive order that is supposed to have ended the practice, she now tells asylum-seekers: “Okay, today if you want to walk across, you won’t be separated from your children, but you’ll all be detained together. You may be deported after 20 days.”While Yznaga stood on the bridge that Monday afternoon, CBP agents let two unaccompanied teenagers cross. Early the next morning, she said, she was told everyone else had been allowed through.Disclosure: The University of Texas – Rio Grande Valley has been a financial supporter of The Texas Tribune, a nonprofit, nonpartisan news organization that is funded in part by donations from members, foundations and corporate sponsors. Financial supporters play no role in the Tribune’s journalism. Find a complete list of them here.last_img read more

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first_img“The difference with YouTube is there is still revenue-sharing going on,” he says, noting his collective’s organically-built following based on streaming cover songs. “Universal Music is issuing mass takedowns of anything they own. The goal is to force Twitter and other social media sites to come to the bargaining table and work out a system of content ID. … Of course, it’s become clear that Twitter DOES exercise control of what gets circulated on on their platform — to the point of reinterpreting their terms of service on a case by case basis — which should require them to be held to the same standards of other media companies when it comes to copyright and liability. But that’s a deeper conversation. The bottom line that I [saw from] my Twitter jail cell, is that when the music industry fights big tech, artists become pawns to be used in negotiation.”A publishing executive familiar with Bradlee’s situation doesn’t disagree, noting, “Twitter does not have licenses to stream music. If Twitter wants to provide its users with the ability to stream music, they should obtain music licenses like other social platforms have done. Further, one would think that a company with a $30 billion market cap would be willing to do the right thing and pay songwriters for their work.” (Twitter did not respond to multiple requests for comment. The company typically does not comment on DMCA takedowns or account suspensions.) Popular on Variety ×Actors Reveal Their Favorite Disney PrincessesSeveral actors, like Daisy Ridley, Awkwafina, Jeff Goldblum and Gina Rodriguez, reveal their favorite Disney princesses. Rapunzel, Mulan, Ariel,Tiana, Sleeping Beauty and Jasmine all got some love from the Disney stars.More VideosVolume 0%Press shift question mark to access a list of keyboard shortcutsKeyboard Shortcutsplay/pauseincrease volumedecrease volumeseek forwardsseek backwardstoggle captionstoggle fullscreenmute/unmuteseek to %SPACE↑↓→←cfm0-9Next UpJennifer Lopez Shares How She Became a Mogul04:350.5x1x1.25×1.5x2xLive00:0002:1502:15 The bone of contention remains that Twitter, and tech goliaths like YouTube and Facebook, don’t want to be held responsible for user content, insisting they’re not media sites but user platforms. That disagreement was addressed in the recently passed EU Copyright Directive’s Article 13, which decrees the sites must begin to police themselves, and will be held liable for any copyright infringements. The U.S. Music Modernization Act doesn’t go quite so far, but copyright lawyer Lisa Alter, a managing partner in the New York firm of Alter Kendrick & Baron, insists it’s a step in the right direction with the establishment of a Music Licensing Collective.“There will be a more streamlined approach to licensing,” she says. “Unfortunately, it doesn’t have provisions for these media sites to vet material.” In other words, the political clout wielded by the Googles, Facebooks and Twitters in the U.S. will make that kind of enforcement difficult until the technology to do so is developed, which should happen in Europe now that Article 13 is being enforced. “Along with the NRA and terrestrial radio, big tech is the most powerful lobby in America,” adds Alter. “It’s a real push-pull to come up with systems that work for creators as well as ISPs [Internet Service Providers]. I don’t think it’s going to happen any time soon.”Bradlee isn’t the only musician currently receiving Twitter takedown notices. His friend and frequent Postmodern Jukebox collaborator Casey Abrams, an alum of “American Idol” season 10 (2011), also had his share of Twitter beefs, ironically for playing Elton John’s “Rocketman” on sitar, which prompted a similar UMPG takedown. Could the company’s legal eagles be sharpening their talons to protect intellectual property anticipating the imminent release of the high-visibility biopic of the same name?In response to Abrams’ violation, Twitter essentially wiped out his account, removing all his followers, and forced him into a new approach to posting his own daily videos on Instagram, Facebook and YouTube. “It’s one less site I have to worry about,” says Abrams, who has a jazz album coming out on May 31st. “It eliminates a lot of stress,” he downplays, noting that, “there’s not a whole lot of love on Twitter.” Musician Scott Bradlee is the leader of Postmodern Jukebox, a collective he formed in 2011 that’s amassed an impressive following by posting YouTube videos featuring vintage jazz, swing and blues covers of pop hits from Lady Gaga and Katy Perry to the Strokes and the White Stripes. With nearly 4 million subscribers, Postmodern Jukebox’s take on songs like Radiohead’s “Creep” (62 million views) and Panic at the Disco’s “High Hopes” have been watched more than a billion times.So when Bradlee received a notice of a copyright violation from Twitter on April 20 for a two-year-old, 20-second-long clip of him improvising the chorus to Elton John’s “Crocodile Rock” on piano (without vocals), it hit him where his own music lived – on the Internet. “I received a Twitter suspension for playing the chorus of Elton John’s ‘Crocodile Rock’ on the piano,” Bradlee told Variety on April 24. “It wasn’t a commercial use and I wasn’t selling it. It was me making a fun recording on my iPhone.” Still, Abrams is perplexed at the ban. “People are posting mean and hurtful things, there’s violence, and we get punished for posting a song with love in our heart? That’s just crazy.”Copyright expert Alter says the music business’ ‘whack-a-mole” method of controlling its intellectual property is a leftover from the 1998 DMCA act. “There’s a whole new industry consisting of companies that get hired by publishers to troll the Internet, particularly YouTube, and find unlicensed music. Then the decision becomes whether to try to monetize through a synchronization license or simply take it down.“The tech industry claims that accessibility should trump copyright protection. Accessible does not translate to free. The beauty of the U.S. Constitution is that it protects original works of authorship, implemented by laws, even as it moves forward to alternate means of production and distribution.”Says Bradlee: “I don’t blame the music publishers; my beef is with Twitter. I just don’t think it’s good for society. You’re going to suspend a kid who makes a cover video for a song just as you would someone issuing violent threats? I’ve come to recognize all the ways our society and brains are being programmed by social media. And this is from someone whose band broke on YouTube.”Additional reporting by Michele Amabile Angermiller  Citing the now-antiquated 1990s-era Digital Millennial Copyright Act (DMCA) takedown provision, Twitter sent the musician a letter it received from David Benjamin, Head of Content Protection for Universal Music Group Publishing “asking for your immediate assistance in stopping this unauthorized activity.” Shortly after the warning, Scott learned from Twitter his account had been suspended “as the result of multiple copyright infringement notifications.” He then took to Facebook to express his outrage. And while he contacted both UMPG, which has since withdrawn the complaint, and Twitter about his account (which has since been reinstated), Bradlee was none too pleased at the hassle.last_img read more

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first_img However, Mansuripur’s bold claim of a paradox with the Lorentz law has generated some intense criticism. One critic, Daniel Vanzella, a physics professor at the University of Sao Paulo in Sao Carlos, Brazil, has submitted a comment to Physical Review Letters arguing that the Lorentz law is perfectly compatible with special relativity, and that Mansuripur has misunderstood relativistic mechanics. The only paradox, Vanzella says, is why the high-ranking journal accepted the paper in the first place.Charge-magnet paradoxThe basis of Mansuripur’s argument is that the Lorentz law violates special relativity by producing different results in different reference frames. According to special relativity, the laws of physics – including electromagnetism – must be the same in all non-accelerating reference frames. He describes a scenario in which a magnetic dipole and a nearby electric charge are located a certain distance apart. When the magnet and the electric charge are at rest, no net force is exchanged between the two. This is because static electric charges only produce electric fields (to which the magnet is oblivious), and static magnets only produce magnetic fields (to which the static electric charge is oblivious). Both the Lorentz law and the Einstein-Laub version give the same result: the magnet experiences neither a force nor a torque from the electric charge.However, the Lorentz law gives a different result when a stationary observer watches the magnet and electric charge in a moving reference frame. Here, the observer sees the moving electric charge exert a torque on the moving magnet, causing the magnet to rotate as it tries to align itself with the electric field. The presence of this torque differs from the observation in the stationary reference frame where there is no torque.On the other hand, the Einstein-Laub formula, when combined with a corresponding torque formula, gives zero torque value for observers in both reference frames, complying with special relativity.The Lorentz law’s incompatibility with special relativity is not its only shortcoming, according to Mansuripur. Another equally important issue is the long-standing problem of “hidden momentum,” in which he shows that the Lorentz law fails to conserve momentum in certain situations involving magnetic media. In contrast, the Einstein-Laub equations show complete consistency with the conservation laws. For Mansuripur, this evidence indicates that the Einstein-Laub formula should be considered as a better way to understand classical electrodynamics. (Phys.org) — The laws of classical electromagnetism that were developed in the 19th century are the same laws that scientists use today. They include Maxwell’s four equations along with the Lorentz law, which describes the force exerted by electric and magnetic fields on charged particles. But Masud Mansuripur, a professor of Optical Sciences at The University of Arizona in Tucson, is now arguing that the Lorentz law of force is incompatible with special relativity and momentum conservation, and should be abandoned. In a recent issue of Physical Review Letters, he has suggested replacing the Lorentz law with a more general expression of electromagnetic force density, such as one developed by Albert Einstein and Jakob Laub in 1908. Best yet test of Lorentz invariance “This work provides a firm basis for all calculations of force, torque, momentum and angular momentum whenever electromagnetic fields (microwave, light, etc.) interact with material media,” Mansuripur told Phys.org. “The electromagnetic momentum and angular momentum become well-defined universal entities (i.e., the Abraham momentum), the need for ‘hidden momentum’ disappears, and satisfaction of conservation laws as well as conformity with special relativity are guaranteed.He explains that, during the past century, there has been a proliferation of equations for force and torque in the scientific literature, with scientists using several different formulas for the electromagnetic momentum. “My paper fixes the foundational equations and allows researchers to compare their experimental results against a single, well-defined theory,” he said.Quantum natureAccording to Mansuripur, the underlying reason for the difference between the Lorentz law and Einstein-Laub formula involves how each equation mathematically describes the quantum nature of electromagnetic fields and media. For its part, the Lorentz law depicts electric and magnetic dipoles as pairs of positive and negative charges or stable loops of current that interact with electromagnetic fields in terms of free and bound charges and currents. In contrast, the Einstein-Laub formula describes material media as spatio-temporal distributions of charge, current, polarization, and magnetization. Mansuripur explains why this distinction is important.“The fact that the electron orbits inside atoms and molecules are stable is a quantum-mechanical phenomenon,” he said. “Neither Maxwell’s equations nor the Lorentz law of force (and nor, for that matter, the Einstein-Laub force/torque equations) can account for the stability of the electron orbit. The fact that electrons, protons and neutrons have a magnetic moment associated with their spin angular momentum is also a relativistic quantum effect that has no explanation within classical physics. What Maxwell’s equations and the Lorentz law (or the Einstein-Laub law) do is provide formulas that describe the behavior of fields and material media as they are, without attempting to justify that behavior. The Lorentz law, however, simplifies the underlying physics by assuming that electric and magnetic dipoles can be treated as distributions of ordinary electrical charge and current. In contrast, the Einstein-Laub equation and the accompanying torque equation treat free charge, free current, electric dipoles, and magnetic dipoles as four distinct constituents of material media.“So, for example, the fact that a magnetic dipole is associated with something resembling a loop of current is a quantum mechanical effect. The Lorentz law does not ignore this fact, but it takes the resemblance to a current loop too far, treating the magnetic dipole as if it were actually a loop of ordinary current. In contrast, the Einstein-Laub formula acknowledges that magnetic dipoles exist as distinct entities – what makes them distinct is quantum mechanics, of course, but Einstein-Laub does not attempt to justify the existence of these dipoles or their nature. The Einstein-Laub formulas then provide a ‘recipe’ for calculating the force and torque on these dipoles, which turns out to be different from the ‘recipe’ provided by the Lorentz law.”No paradox?One critic of Mansuripur’s ideas, Vanzella, thinks that the paper is so flawed that it should not have been published at all. In his comment submitted to the journal, Vanzella points out that the Lorentz force can be put in a covariant form. In special relativity, a covariant law cannot lead to incompatible descriptions of the same phenomenon in different inertial reference frames. He explains that Mansuripur has incorrectly used relativistic mechanics and ignored a hidden momentum that makes the Lorentz formula predict a torque in one reference frame but not another. “This has blown way out of proportion,” Vanzella said. “Let me begin by stating the most important point: there is no incompatibility between the Lorentz force and special relativity. This is not a matter of opinion: any relativist knows that this is impossible for any specially-covariant law (as is the Lorentz force). By construction, a specially-covariant law is compatible with special relativity. This means that if it leads to a satisfactory description of a phenomenon in one inertial frame, then it leads to consistent descriptions in any inertial frame; there are no paradoxes.”He added that apparent paradoxes appear frequently when dealing with special relativity, but these paradoxes are actually due to simply missing or overlooking part of the relativistic argument. He says that a very similar “paradox” to the charge-magnet paradox, called the Trouton-Noble paradox, was presented and resolved more than 100 years ago. “In this particular case, using a current loop in a perfectly-conducting ring to model the magnet’s magnetic moment, one has to use special relativity to show that, even when the ring is at rest, the total momentum of the system is not zero (when subject to an external electric field),” he explained. “This momentum has been termed ‘hidden’ in the literature and this has led to some confusion, but let me stress that it is real momentum. Mansuripur is missing the point that this momentum is not an ad hoc invention only to solve paradoxes; its existence is forced upon us (upon Nature, actually) due to the principles of special relativity alone. In my comment I do not postulate the existence of this momentum. I simply use special relativity to calculate it; no additional hypothesis other than special relativity and the Lorentz force. Therefore, when Mansuripur dismisses this ‘hidden’ momentum he is doing exactly what I said is needed to arrive at a paradox: missing or overlooking part of the relativistic argument.”Despite his strong disagreement with Mansuripur, he emphasized that his criticism does not suggest anything against Mansuripur’s scientific credibility.“Please note that I don’t think that Mansuripur not knowing the solution of the ‘charge-magnet paradox’ (or not understanding the given solution) is that bad,” Vanzella said. “Special relativity is certainly not his expertise and confuses a lot of people, even physicists.”He also added that he’s not necessarily arguing that the Lorentz law must be the correct law of force, either, but just that special relativity cannot be used to testify against it. The question of which law is correct is an experimental issue. Still, he’s adamant that there is no paradox in this situation.“I wouldn’t even call Mansuripur’s idea ‘controversial,’” he said. “Would you call ‘controversial’ the idea that the Earth is flat? It is simply and provably wrong (I mean the claim that the Lorentz force is incompatible with special relativity).”In a response to Vanzella’s comment, also submitted to Physical Review Letters, Mansuripur has stuck to his original argument, explaining that there is no need to introduce hidden momentum, and that the Trouton-Noble paradox was subtly but significantly different than the charge-magnet paradox.Future of Einstein-LaubDespite the advantages of Einstein-Laub formula, Mansuripur acknowledges that it is not without its own problems. In 1979, physicist Iver Brevik performed an extensive review of the Einstein-Laub formula and other possible candidates for an energy-momentum tensor for the electromagnetic field. In some of the experiments, the Einstein-Laub formula did not match actual observations as closely as another formula, the Helmholtz force equation. However, Mansuripur argues that, due to the potential significance of this idea, the contrary evidence deserves a closer examination.“My colleagues and I are currently trying to identify situations where the distinction between the Lorentz law and the Einstein-Laub formulation is unambiguous, then try to conduct experiments to determine which law is operative in such situations,” he said. “Personally, I don’t attach much significance to the historical evidence against the Einstein-Laub formulation as reviewed in the paper by Brevik. The experiments were all electrostatic experiments, involving the flow of some dielectric fluid into a capacitor. The theoretical methods used to analyze the problem were extremely confusing; many approximations were made, and the Einstein-Laub formula itself was never used directly; instead they used a stress tensor associated with Einstein-Laub, which I have shown elsewhere to be incorrect.Mansuripur also plans to further investigate what he thinks has been a much overlooked distinction between the two formulas: a term that describes the force density of an electric field acting on the polarization density of a material medium. Whereas the Lorentz law uses –(del.P)E, the Einstein-Laub formula uses (P.del)E. Although the two formulations give exactly the same total force and total torque on any solid object, differences emerge when dealing with soft objects.“If applied to soft objects such as biological cells under intense illumination or droplets of oil or water in optical tweezers, the two formulas give different force and torque ‘distributions’ throughout the object,” he said. “This difference in force/torque distribution will then manifest itself in different deformations of the object under intense illumination. Our near-term goal, therefore, is to look for deformations of soft objects in optical tweezers experiments. A long-term goal is to look for observable differences between Lorentz and Einstein-Laub in magnetic materials.” This document is subject to copyright. Apart from any fair dealing for the purpose of private study or research, no part may be reproduced without the written permission. The content is provided for information purposes only. Charge-magnet paradox: the point electric charge q and the point magnetic dipole to its right are separated by distance d in the x’y’z’ frame. An observer in the x’y’z’ frame sees no torque, but a stationary observer in the xyz frame watching the x’y’z’ system move with constant velocity along the z axis sees the moving electric charge exert a torque on the moving magnet. Image credit: Mansuripur. ©2012 American Physical Society More information: Masud Mansuripur, “Trouble with the Lorentz Law of Force: Incompatibility with Special Relativity and Momentum Conservation.” Physical Review Letters 108, 193901 (2012). DOI: 10.1103/PhysRevLett.108.193901 Explore further Copyright 2012 Phys.org All rights reserved. This material may not be published, broadcast, rewritten or redistributed in whole or part without the express written permission of PhysOrg.com. Citation: Is a classical electrodynamics law incompatible with special relativity? (2012, May 24) retrieved 18 August 2019 from https://phys.org/news/2012-05-classical-electrodynamics-law-incompatible-special.html Journal information: Physical Review Letterslast_img read more

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